Killer Instinct

All the "friendly" achievements are currently bugged in a good way; you need only finish an exhibition match vs. anyone. Win or Lose, the achievement will unlock at the end of the match, unless your opponent disconnects.

So jump into exhibition matches, pick Tusk, finish the match, and then pick "select character" so you can get another friendly achievement. No friends or skills required.

The Exhibition mode is the online mode where you can create or join a private room and fight your friends. Unlike Ranked matches you can invite people to the rooms that you create, thus making this achievement incredibly easy to boost.

All you need to do is create a room, invite a friend and win a match.