Dota 2

Valve's 2013 MOBA is the most mechanically unforgiving game in wide circulation, and it is free with every hero unlocked from the first match. Two teams of five push lanes toward each other's base; everything else is detail, and there is an enormous amount of detail. Over a hundred and twenty heroes, none of them balanced against each other in isolation, denying your own creeps to starve an opponent's experience, couriers, wards, camp stacking, and an item shop where the right cheap purchase beats the wrong expensive one. Matches run forty minutes and can be lost in the first ten or won in the last thirty seconds, because buybacks and Aegis mean no lead is safe. Its other significance is competitive: The International's crowdfunded prize pool repeatedly broke esports records, peaking above forty million dollars, funded by players buying a battle pass. The learning curve is genuinely brutal and the community's reputation is deserved, but nothing else offers this much strategic depth per match.