nice guy

Short definition from Wiktionary

Noun

1. 1
   An inoffensive adult male who desires romantic companionship but who is too bland and uninspiring to be attractive.
2. 2
   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.
3. 3
   Used other than figuratively or idiomatically: see nice, guy.