League of Legends, and DOTA 2 (Defense of the Ancients). Two of the biggest games in the current (still debatable, according to some people) in the Action Real-Time Strategy/Multiple Online Battle Arena genre. However, it wasn't all smooth sailing between the two communities at the beginning, with a history between the original DOTA and League of Legends spanning since the inception of the latter (for more history, google Pendragon and Dota Allstars. This may give you a picture of what has happened).
But as both player bases reach soaring heights, and tournaments where professional players compete for nearly millions of dollars, should we care about two games crowding the genre stratosphere? Should there be only game which reigns supreme? If you're a player of both games, should you actively root for one game, and just outright refuse to play the other?
The answer is no, and at this stage we should simply focus on the gameplay and entertainment of the game. League of Legends is by far the game that I would play with my friends (especially my girlfriend), as it's much easier to get into. DOTA 2 I find a more strategically rich game, with a more open pool of heroes and increased item choices that expand the strategies a team may take.
At this stage, I don't care about either companies' skeletons in the closet, or what transgressions may have happened in the past. Yes, a community may have been destroyed due to an individual's actions, but in this current day we should celebrate the merits (and criticise the weakness) within each game, and enjoy them for what they are - games to enjoy with friends.