i mean it doesnt have to be anime conventions its usually any kind of gathering where said yopic. of convention has a gathering of introverts, in particular, ones that have 0 sense of self awareness.
in terms of worst to less worse:
Card game tournament(sweaty, generally lack of AC, small venue cause cheap) < Video Game tournament (similar but in a room full of electronics, usually helped out by that their venue is larger) < anime conventions