Tron: Evolution

This one is kind of misleading. You need to actually deliver the final blow with the Stasis Disc, meaning that the Y, RT + Y, and LT + Y must actually derez the enemy, instead of just hitting them with stasis and killing them normally.

Go to multiplayer and create a match. On the game mode setup pick Private Match, Disintegration, Heat Sink, 10 players, 20 minutes and 100 points.

When you start make sure your Stasis disc is on :)

Attack the other players and wear their energy down, just make sure you kill them with stasis kills (Y, LT+Y or RT+Y).

Make sure you keep topping up your charges. The easiest way is to pick up the Overcharge which is high up and looks like a double helix DNA symbol. This will fill your charges to the maximum.

I know this game has been around for a while, and doesn't have a huge following, but after seeing the other solutions, I felt I had another solution that works just as well, if not better. For those who still play, I think this approach will help "version up" (this game's way of "leveling up"), and help you blow through the Story mode on a harder difficulty to get those achievements too. Here goes:

1) Go into MULTIPLAYER
2) Go to CREATE MATCH
3) Go to GAME MODE SETUP
4) Set MATCH TYPE to PRIVATE MATCH
5) Set GAME MODE to DISINTEGRATION
6) Set MAPS to one of the following: HEAT SINK, HARD DISK, SPIRES, or SKYLINE (the last 2 are DLC, and all 4 maps do not allow Light Cycles. If a map allows Light Cycles you can't play against NPCs/Bots)
7) Set MAX PLAYERS to 10
8) Set TIME LIMIT to whatever you like based on what you set SCORE LIMIT to in #9
9) Set SCORE LIMIT to whatever you like in terms of how many derezzes (kills) you want to get
10) Hit Y to start the match.
11) Press up on the D-pad to activate the Stasis Disc. Only use the Y button for your attacks. Remember this is a special disc power you will need to recharge this often. You must get the derezz of the enemy using Y.

I have found this method quickest to the 25 derezzes, as well as a way to version up rather quickly, gaining those MB to perform SYSTEM UPGRADES quicker (thus unlocking the achievements related to these quicker as well). In addition, by versioning up and upgrading while doing MULTIPLAYER, your version and upgrades will carryover into the STORY mode, thus allowing you to go through the story on a higher difficulty to get the story-related, and difficulty-related achievements easier.

The above method can also be used for the achievements related to the other disc mods (Bomb, Corruption, and Heavy) as well. You can do all this in a PUBLIC MATCH too against other players, that is of course if you can find one (lately there seem to be a few people on playing which is more fun than just bot bashing). Just remember, up on the D-pad and Y are the keys here.