I just finished grinding through this achievement and thought I would share what I learned about the different medals and how some of them unlock. I posted some of this on the Halo Waypoint forums and copied that over to here and expanded on some other areas.
Please note that if you are going to try and do this legit it will take you a lot of time and there is a chance your progress may regress at some point. My progress was set back 23 medals in the middle of me going for this and I’ve heard of even worse regression from other players. It’s incredibly frustrating when that happens! I’ve read that it has to do when the playlists are updated but I have not confirmed that.
Domination is rewarded for getting 100 Legendary medals in multiplayer matchmaking. You can see which medals are legendary by hitting start, going to “Career” and then over to “Medals.” The Legendary medals are the first six medals listed. Now what I’ve found is that some of the medals are listed incorrectly for what games they will unlock in.
I finished with the following medals: 1 Extermination, 1 Perfection, 52 Steaktaculars, and 69 Triple Doubles.
I did not obtain any Killionaires or Unfriggenbelievables so I can’t speak as much about those medals. I’m going to leave out the descriptions for each medal as Epilepsy Sucks has already documented that, but I will say what I learned about each medal.
- Exterminations: This one should work in all games but I've only gotten one in Halo 3 while playing Swat.
- Killionaire: Should work in all games? This one I'm not sure on since I've not gotten one but since the multi kills track the same in each game I would assume this one
works in all games.
- Perfection: Does not work in Halo 4 due to it being a commendation in the original game and not a medal. Should work fine in the others but I've only gotten one in Halo 2A.
- Steacktaculars: Work correctly in Halo 1 and Halo 2A. I've heard they work in Halo 2 Classic but only if you get 20 kills. I don't know how true that is and haven't been able to confirm it. They do not work in Halo 3 and 4. My guess is they were always awarded on Bungie's website in Halo 3 and never in game so that code wasn't there and it was never added in. Same goes for Halo 4 where they were never an in game medal and it wasn't added in MCC. This is also my thinking on why assists in Halo 3 don't count towards the assist achievement since there was never a medal for them even though it is tracked.
- Triple Doubles: Most likely it does not work in Halo 3 as it was another medal that was awarded on the website and not in game similar to the Steaktaculars but I can't confirm it. They do work in Halo 4.
- Unfriggenbelievable: I've never gotten one of these either but the medal chest says it works for all games except Halo 3.
None of these medals need to be obtained in a ranked playlist, but I did get most of mine playing ranked.
Originally when I started going for these I thought Steaks would be the easiest ones like Epilepsy suggested and was doing this in both Halo 2A and Halo 1. Along the way I got a few triple doubles in Halo 2A but it was difficult to get the headshots and assists needed. I've changed my opinion on that and have found that Triple Doubles are a much more repeatable medal to get in Halo 4. I played the ranked Halo 4 playlist and recommend either regular Team Slayer or Capture the Flag/King of the Hill as they are usually longer matches (Team Slayer goes to 60 instead of Legendary Slayer which goes to 50) giving you extra time to get the assists/headshots. It’s also much easier to do this with a couple friends as you can call out who you are damaging and they can finish them off for the assists. Even while playing with random players I have managed to get 10-12 medals in a night of playing whereas before I was getting around 2-4 Steaktaculars in a similar amount of time.
As a reference for my skill level, I’m an 18 in Halo 2A, a 10 in Halo: CE, and a 20 in Halo 4. Those are the three games I got the bulk of my medals in. While I wasn’t able to get a Triple Double every game, I did get them much more consistently than Steaks. As an added bonus the Halo 4 games also seem to go a bit faster! Assists are the easiest by far to get in Halo 4 and while it takes a few games, you should get the hang of how much damage you have to do to get credit for the assist.
My main loadout in Halo 4 was: BR, Magnum, Frags, Active Camo, Mobility, and Ammo.
Use a loadout that you’re comfortable with but you will want precision weapons (BR, DMR, Carbine, Light Rifle, Magnum) to get those headshots.
I hope this helps some people out and if there is anything wrong with the guide please let me know and I will correct it! Also, if you vote negatively on this let me know too! I appreciate the feedback as this is the first guide I’ve written.
TLDR: Triple Doubles in Halo 4 are the way to go for this achievement as they are a more repeatable medal than Steaktaculars. Good Luck!