Halo: Combat Evolved Anniversary

Okay this achievement basically requires you to play the level "Two Betrayals" only using the Plasma Pistol and Shotgun on Legendary. This one's difficult to couple with the "Look Out for the Little Guys" achievement from the same level as one requires you to play conservative while the other requires you to be careful and not kill Grunts.

SOLO:
The easiest way to do this on solo is to equip the Bandanna skull and utilise the shotgun against the Flood and in close quarters while using grenades against enemies from afar.

The hardest part for me was just after leaving the tunnels and beating the Flood + Covenant forces before the last Generator. Use overcharged Plasma Pistol shots against the Banshee till it eventually goes down and patiently throw nades and let the enemy forces take eachother out.

So i discovered a really good way to counteract the inability to "Revert to Last Save" by instead hitting "Save and Quit" on the pause screen at regular intervals (as you require). This means if you pick up a weapon by accident you can just save without quitting (Dashboarding/Turning off the Power) and then continue from your last save point with the mistake forgotten.

The best part about this is that it will work for every mission specific achievement, in particular:
- Beat The Library on Heroic without dying
- Finish the Maw Countdown without exiting your hog
- Finish a level without losing health damage

I don't want to post a guide for each achievement and flood the pages with repitition but note that it can be used in all these cases if you are having trouble.

COOP: This makes it much easier. Have a secondary controller on split screen or a friend over XBL lead the charge with the Rocket Launcher nd Shotgun while you sit back and get an easy chiev. Bandana is always a help!

Good Luck!

I did this with a partner which made it easier to deal with however it is not impossible to do it alone. simply play the level as normal and stick to the items you have if you die it still counts as long as you don't pick anything up.

You should equip the bandanna skull so you have infinite ammo. just take it slowly and use a lot of grenades and you should be able to manage this easily.

This is a personal achievement as long as you never pick up a weapon it should proc, even if you spawn with new weapons.

EVERYTHING DONE FOR THIS ACHIEVEMENT IS DONE WITH A SECOND ACCOUNT DO NOT USE YOUR MAIN ACHIEVEMENT ACCOUNT AT ALL EXCEPT FOR PART 7 ALSO IT IS A GOOD SPAWN DUMMY

Map - Two Betrayals
Difficulty - Legendary
Players - 1 (but 2 accounts)
Achievement Difficulty - 7
Skulls - Bandanna (infinate ammo)

I have some tips on how to do this by yourself split screen
1 - set up another account and play split screen
2 - once the game loads play on the other account and leave the account that is getting the achievement in the back. (Simply DO NOT TOUCH the account getting the achievement for now)
3 - Once you get to the door in the beginning that you have to open press X or B to open and once the game freezes for a second press X or B again and this will glitch out all the enemies but 1 elite.
4 - Take out the wraith and grab a banshee and fly back to wear you opened the door. Press X or B again to close it then open it again and this will spawn all the enemies now just jump into your banshee (ignoring the enemies) and fly to your objective.
TIPS - the other account that is not going for the achievement also the one getting all the kills and doing all the work CAN pick up new weapons, and kill grunts.
5 - Go through the level like you normally would do and you achievement account will spawn in a safe area every time and you can use this as a spawn dummy.
6 - Try finding a rocket launcher because this will come in handy when you have to fight out side. If you have infinate ammo just keep shooting your rockets at anything that moves outside. Try to take out the banshees first.
7 - This is the hardest part about the achievement. Once you clear out the room and are in the 3rd controll room where you have to step into that thing and loose your shield.

Once you clear out all the enemies take your achievement account and walk into the room as well. Take your second account (the one doing all the work) and go through the door with a rocket and aim down the hallway. Now let your main account walk into the beam and then immediately take your second account and shoot a rocket at all the enemies that will spawn next to you. (this will kill you)
Once your main account has activated more enemies and your shield goes down go to the back of the room and kill everything you see and just hope your second account can spawn in time. DO NOT PICK UP ANY WEAPONS WHILE YOUR SECOND ACCOUNT IS DEAD


THIS MAY SOUND CONFUSING BUT IT REALLY IS NOT JUST STEP 7 TAKES A COUPLE TRIES. I WILL MAKE A VIDEO SOME DAY TO EXPLAIN IT A BIT BETTER.

8 - Now you are pretty much done with all the hard stuff take your banshee and fly through the tunnel without killing anything and try avoiding the rockets. Once you get pass all the enemies your main account should spawn next to you. Now get out of the banshee and head back killing the 2 - 3 rocket guys and then there will be a ghost that you can grab. Get that and head back to the objective.
9 - Open the door and kill off the enemies that come through then back your ghost in through the door and then take your banshee and push it through. DO NOT SKIP ANY ENEMIES AT THIS PART
10 - Now just take your ghost and skip past all the enemies WITHOUT FIRING and stay as far right as possible. Once you get to the finale banshee take it and swirl upwards and then head towards the objective and take out the robot things flying around by the door.
11 - Go in the door and quickly get the objective and mission complete

I WILL PUT OTHER PEOPLES VIDEOS UP ON SOME TIPS I WAS MENTIONING NOTE NONE OF THESE VIDEOS ARE MINE BECAUSE I DON'T HAVE ANY UP YET AND REMEMBER THE SECOND ACCOUNT CAN KILL GRUNTS AND PICK UP NEW WEAPONS =)

Just a quick tip for co-opers. If you die in co-op it does not void this achievement. I was playing the level while a friend kept back to get the grunt achievement and while I died many times I never switched my weapons and I got this achievement