oh wow

Mine would be defeating (FF Tactics spoilers) Wiegraf/Belias in FF Tactics, that fight is really crazy

I beat Hardcore on Minecraft with a buddy x ) Felt really proud of that.

Beating Ghosts 'n Goblins (NES) twice in one session. The game has haunted me for years, and to conquer a game that I had told myself repeatedly as impossible was such a major accomplishment.

Other than that, I guess I could say 100% on all trophies in Killzone 2 (Including DLC). The multiplayer gave me some frustration as well as some tedious objectives, but to beat Killzone 2 on Elite was satisfying after that final push in the last chapter (Reminds me of Heart of the Reich from WaW).

Not really proud of gaming achievements, as somebody is always better so..

Probably beating Tales of Symphonia 5 times but still enjoying and replaying the game to this day (but not as frequently, obviously)

Dang, I need to work on my achievements. I haven't platinumed or 100%ed anything. lol

My biggest accomplishment is beating the Ninja Gaiden games on NES. (Don't judge. Those games are hard as shit.)

Completed F Zero GX 100%.
When the game says Very Hard, you better believe it is Very Hard.

You beat the hardest game in the history of video games. Please accept my kudos! 

I beat Resident Evil 5 on the hardest setting...single player. Sheva was a greater adversary than any mutant zombie ever could be.

When I was a child, I was playing SW Battlefront II. I thought it would be fun to play in the hardest difficulty in single player, so I started a game in Geonosis as a CIS sniper. So, in five minutes or less, my whole team gets slaughtered and they are unscratched, I'm the only soldier left. So I start moving all around the map, making stealth attacks and trying not to get killed, and making the NPC allies kill the enemies. It took me almost an hour into beating every single enemy soldier, getting my victory. An hour of sniping, hide and seek, and other tactics. After I finished that game I was exhausted, but it was woth it. I have never being able to replitate that game.

Double-killing 2 lvl 22 players on LoL with Nassus (I was lvl 8)