The Orange Box

To grind this out, have you and another player start up a Player Match (make sure to turn on the maximum amount of private slots so randoms don't join, as well as setting "No Time Limit") and be on the same team. Have the player NOT going for the achievement choose a Soldier and stand in a corner of the spawn room, while the player who IS going for the achievement be a Medic. The Soldier stands in the corner and continuously fires rockets to injure himself, and the Medic will need to hold down RT with the healing gun thing (rubberbands work wonders so you can go do other things) to constantly heal. When the Soldier runs out of ammo he can simply walk up to one of the cabinets in the spawn room and replenish it. Shouldn't take more than 20 minutes or so, probably quicker.

Special thanks to DragonYen for the advice!

Note: The game will not keep track of the heal points you've acquired in realtime with this method. LEAVE the spawn room, hit Select, and choose another class to kill yourself. The heal points you've acquired will then be tallied on your achievement screen :).

Easy. Just jump into a ranked or player match and be the medic and just heal people the whole game, most preferably heavys and soldiers since they have the most health and will net you more healing points.

All together it took me just over an hour of playing to get this achievement but depending on how much you are healing it could change but I would say on average it should take 1-2 hours.

To begin, join any game of your choosing, ranked or unranked, and select your favorite map. For the sake of getting the achievement, I would suggest Dustbowl, as there is a constant area of combat where the people you will be healing take constant damage. By far, the best way to get the achievement is to find a Heavy, and have a constant healing beam on him as he gets torn apart by the enemy. Soldiers also work, but Heavys are much better, and people who play as them put themselves into the line of fire, allowing you to jump in and build up healing points. When there are no Heavys around, heal all friendlies around you until you spot someone who looks as if they are charging the enemy. You will most likely get this achievement naturally while playing, so a lot of effort really isn't needed. If you were to really go for just this achievement, I would guess it would take about an hour and a half to obtain.

To add onto the solutions on here, you can not check in real time how many points you have healed under "My Achievements", but if you press the "Y" button and bring up the in-game leader board, you can see how many healing points you've acquired in real time. You can leave this up while you are healing as well, so that you don't have to keep toggling back and forth.

Also, Ubercharging while you are healing adds about 10 points a second to your heals, so use it as soon as you get it. (If you leave the leader board up while healing you won't be able to see when Ubercharging is available, but you can simply hold down both triggers and it will activate as soon as it's possible).

Once you've reached 25,000, you will need to get killed for the achievement to pop. (If you haven't left home base to boost, you might be able to get it to pop by changing classes twice, I tried killing myself by changing classes 1 time, but since I hadn't left the base I stayed alive for the class change. I changed classes again back to medic and it popped. Weird, but it worked somehow.)

Play private/systemlink, 2 players.
As usual, one medic and one soldier on the same team (2Fort).
Do not leave the spawn area, but have the soldier stand besides the resupply cabinet in order to get a constant supply of grenades.
Have the medic stand away from the soldier and start healing the soldier. While healing (RT) press the XBOX Guide button to open the XBOX Menu. Release RT and you will continue healing.
The soldier now can shoot grenades at his feet in order to get damage. Make sure that your back faces the resuply cabinet and the wall, so that the backblast does not move you away from your spot. Same as above, while shooting at your feet, press XBOX Guide button and release RT. You will continue shooting damaging yourself. Due to being close to the resupply cabinet, you will get infinite ammo. Get some coffee and when you return your medic will have enough points. Make sure to die once as the medic in order for the healing points to register.

This is a very simple acheivement, but it takes some time. It took me around 1-2 hours to get 25000 points. What I did was a friend and I made a match on 2fort and he played as a heavy and me as a medic. We then would go rush the other team's base and usually the sentrys would try to take out the my friend but I would continue to heal him then ubercharge him to take ou the sentrys. On average I got 5000-7000 points a game.

So an easy way to do this is to host a player match with 8 players and make all 8 slots private. Then invite a friend and go to 2fort. Make sure you are both on the same team and hop into the lake/river in the middle and you both submerge yourselves. Face each other and start healing each other. As you continue to heal each move into a corner. You will both be occupying the same space so it will appear your 2 characters are inside of one another. Once you are in the corner look down. This should prevent you from drifting when you take damage. Now just heal away. It only took me about an hour and a half, maybe an hour and 45 minutes to get this using this method. You tend to drift a bit so rubber banding may not work, my friend managed to do it with only surfacing by accident once or twice, so you can try to do it while doing something else and just check back every few minutes.

This method takes a bit longer than the soldier-doctor combo but since you can rubber band your controller for it with checking in every now and again I feel like it’s much more painless. You also don’t have to worry about accidently getting blown up as the medic. You can also get it simultaneously with a friend which comes into account as well since you will both unlock it in this time period.

NOTES: You can check your heals for the round by pressing Y and it will update in real time. The achievement will not pop until you die, so press Y to check and once you hit 25,000 stop healing each other and allow yourselves to die.

Another thing to note is do NOT activate the ubercharge for this method. It will prevent you from taking damage from drowning and actually slows down your progress.

Here's a boosting method...

Grab two friends (three including yourself) for this achievement and join a closed game. One player on the other team will stand-by doing nothing, one will be a medic going for the achievement leaving the last person as a soldier. The soldier will run in a corner near yours and his spawn shooting a rocket against the wall or floor causing damage to himself. The medic getting the achievement will heal while the soldier does this.

If the soldier runs out of ammo he/she can run back into spawn (or attempt this within the spawn) and grab more ammo. Once the medic gets the achievement alternate positions with someone else.

Hope this helps!

On 2Fort, follow a teammate or friend playing as the Heavy and continuously heal him, building up your Ubercharge to use in case either of you take on a lot of damage.
**If you're fortunate enough to run into the opposing teams' turrets, take cover, and have the Heavy duck in and out of cover as you heal him.

I did this method legit on 2Fort, a 45 minute game, and totaled about 9000+ healing points. Though this also includes healing my teammate in regular combat and results may vary.

This works great in a 1v1 unlimited time setup. Following what others said, take soldier and blast yourself in the corner while the other person heals as medic.

Healer - find a safe spot where you can heal and not take rocket damage, and then rubberband your trigger while the soldier damages himself and resupplies. You can hit start and go into the achievement section to see how much you had previously healed, and then once you have that figure, pull up your in game stats, and do a quick subtraction to figure out how far you have to go. Once you're sure you're over 25k between both screens, switch class (kills you, and ach pops) and switch over to the soldier so your friend can snag the ach.

This achievement can glitch out very easily. What I did with several people is to both start on the same team but make sure that as soon as you spawn you both run out to the middle of the map, then back to the re supply room.

Once you are there, the soldier will stand in the corner next to the supply cabinet and shoot rockets at their own feet. While the medic holds RT to heal.

Once the medic reaches around 5000, have them exit to the middle of the map and change classes (to make sure the points are counting).

The most important part, however, is as soon as the medic reaches 25000, they need to leave the room before dying. If you don't leave, the achievement may glitch to say 25,xxx out of 25,000 and not unlock.

If this happens, just finish the game.

To fix this glitch, start a new game on the same team again. Have the medic get around 100 healing points in the middle of the map. Then, have your soldier switch teams and kill the medic. Achievement unlocked :)

Just to add an easier quicker boosting method for 2 people. If you and a boosting partner both want this achievement, you can easily get it together at the same time.

Firstly start a player match on 2fort and both play as medics on the same team, then both run and jump into the water in the centre of the map and start drowning. Both players should start drowning and thats when you start healing each other. So either rubber band the trigger down or just go to the 360 dashboard (when dashboarding, the buttons you are holding at the time will continue working) and wait for about 40 - 60 minutes and both players should unlock the achievement.

Just to note that it is a good idea to position both players in a corner of the water area together, inside each other facing down as the characters can get pushed away.