I think even more infuriating than blatant hacking is this epidemic of "micro cheating" for lack of a better way to put it that I've seen prevalent in some games that just boost some stats or reactions by amounts large enough to help the cheater but low enough where new or inexperienced players have absolutely no way of telling if someone is cheating or genuinely good especially in games with high skill ceilings. At least when it's blatant you can leave without time wasted but when they're doing it subtly you end up getting tilted and spending the whole match with a bad taste in your mouth second guessing if someone is actually playing fair or not. Chivalry 2 is a really bad offender for this, once you notice it you can't unnotice it anymore, almost every match will have at least one guy with his swing/move speed adjusted by ~10% and in a game where swing manipulation is a legitimate mechanic it can be borderline impossible to catch someone out on it unless you're really paying attention.