toxic bachelor
n. An unmarried man who is selfish, insensitive, and afraid of commitment.
I hope no one gave you The Rules for Christmas, girls, because I'm afraid that the idea that men could be brought to heel, like dogs, is completely over. There is a triumphalist whiff of testosterone in the air — the toxic bachelor, formerly known as the cad, the rake, the bounder and the ladykiller, is back in town.
—Jane Campbell, “Watch out ladies — the toxic bachelor is coming to town,” Independent on Sunday, January 06, 2002
1995 (earliest)
Carrie's brother Peter (John Barrowman) is an attorney whose glamor-boy aura and family mystique obscures his professional achievements. His best friend, Gil Chase (Justin Lazard), is a sleazy, love-'em-and-leave-'em stockbroker, accurately described in the pilot as a "toxic bachelor."
—Gene Seymour, “New York City gets its own prime-time soap, 'Central Park West.',” Newsday, September 03, 1995
This phrase was coined by Candace Bushnell in one of her original "Sex and the City" columns for the New York Observer in the mid-90s.