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. It doesn't matter who hosts the match.

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