For this achievement you must defeat both bosses in Arcade mode on the hardest difficulty. The 2 final bosses that can be faced in the game are Akuma and Orge. The final boss fight will take place on the 7th stage of Arcade Mode after you defeat Jin and Xiaoyu. This achievement will require 2 playthroughs. The boss you face depends on the primary fighter you select for your team. If you have a Street Fighter character as your primary then Orge will appear in the final match. And if you have a Tekken character on primary then Akuma will appear in the last match. The second character in your tag team does NOT matter. With this being the case, you can easily run through Arcade Mode using Zangief for these 2 playthroughs, one with him as your primary and another with him as your secondary character (have a Tekken character as your primary for this playthrough).
When starting up Arcade Mode play under the following settings to make matters significantly easier and faster for you:
Rounds to win: 1
This method is extremely useful since you will no longer have to endure prolonged battles plus you can simply spam Zangief's moves and still come out with easy wins within 30 seconds. When using Zangief you want to use his 2 most effective moves: Double Lariat (), Flying Powerbomb ( + ) & Spinning Piledriver ( + ). Double Lariat is easily one of Zangiefs most abusable moves and you can continue to spam it as your opponent gets up. The Spinning Piledriver is his command grab and does damage depending on the punch button you press. However if you are having trouble performing the 360 commands or if you are too lazy you can equip Zangief with the Super Easy Input Assist Gem so that you only have to press + to perform his Piledriver at the cost of a 10% damage reduction.