nice guy

(euphemistic, idiomatic) An inoffensive adult male who desires romantic companionship but who is too bland and uninspiring to be attractive.
(Internet, derogatory, sarcastic) A man who pretends to be kind and polite with the goal of attracting women, often becoming hostile and misogynistic when their advances are rebuffed; someone affected by nice guy syndrome.
Used other than figuratively or idiomatically: see nice, guy.