> "Adversary" is a weaker word that is more apt

> Words matter, at the very least to avoid starting nationalistic flamwars here on HN.

I agree!

Back in Arcade Machines time, when a player is busy playing a fighting game, Street Fighter, I guess, and another person inserts a coin to play against him, the game pauses and a message that reads "Here's come a new challenger" pops up, so I think challenger would serve the purpose somehow!