This one, the first version. Only one rule that was suppose to make it play defensive, unfortunately this rule had one unintended consequence which make it broken.
Here it plays at 2500 elo getting destroyed vs a 1000 elo Stockfish, one of many matches. In fact I never saw this bot winning any match. The rule is just too restrictive even against a player not knowing/exploiting it. If you know the rule, I suppose someone just discovering chess could win against the bot at 3000 elo.
Well, both Chess.com and Lichess bots are technically capable of resigning, though it's rare. Bots can be programmed to resign under certain conditions: the Lichess API allows users to create custom bots, so theoretically someone could create a "resign-on-capture" bot, however I don't see any evidence of one currently existing. I'm surprised nobody has made one yet, it's such a funny concept ! It would be perfect for beginners who want an "ego boost" or simply for laughs. Ciao
Wait bots can resign?