There are 12 achievements worth 120G for completing 500 games and there are 11 achievements worth 105 G for winning 500 games. In total there is 23 achievements worth 225 gamerscore for playing/winning 500 Custom or matchmade games for Halo: TMCC. This is a guide to obtain all of those achievements, plus I will list off all multiplayer achievements you can do in custom games, organized in what the requirements are to doing them.
The first thing I need let you know, if you plan on doing ALL multiplayer/custom achievements you should unlock the ones below first because they will give you progress towards the wins/games played achievements (it can save you 30 minutes to and hour by doing these first)
(Read walk-through first before doing these, then use the method to get these)
This achievement will give you games won/played towards all 23 achievements, if you don't want to and just knock these out of the way then follow this guide!Walkthrough for multiplayer wins/played
Edit 08/21/2015: M E T H 0 D Man
I don't know if anyone has mentioned this but it is still possible to end the game early on forge and have it count as a victory. I tested it with halo 2,3, and 4.Ham Man 89
Halo 2 anniversary custom. Lockout, slayer, start game. pause and end game after match loads. works solo. halo 3 custom works... halo 4 also works... just quitting out as soon as u can
This isn't the only multiplayer achievements that can be done in Custom, I have compiled a list of all the achievements and what you need to get them. Take a look:Needed: 1 controller (can be done all by yourself):
Needed: A willing friend or 2 controllers:
Needed: A willing friend or another controller (best done in forge)
Needed: 2 willing friends or another 2 controllers
Needed: a willing friend who has the Legendary Anniversary achievement:
I hope this list helps everyone into doing all multiplayer that is achievable in Custom matches, I finished them yesterday and its good to know I don't have to play multiplayer anymore if I don't want to.For this last achievement you can do it with another friend (having 3 controllers in total meaning one of you having 2 controllers in possession).
Having 3 controllers and doing everything yourself which would be extremely difficult
Having 1 controller and splattering an enemy in Campaign (extremely difficult also)
If my guide to all custom multiplayer achievements has flaws or can be improved please comment or message me and I will fix it immediately.
Good luck to everyone and have fun!