Hozzer

a person with relationship tunnel vision who predictably ruins every relationship he or she enters in exactly the same pattern/way. A hozzer is a serial monogamist who completely and totally devotes himself to every new girl he dates. However, within a relatively short period of time, he realizes that in fact he will not marry the object of his affection, and he aggressively begins ignoring his relationship duties until the relationship falls apart and an awkward breakup ensues. The object of a hozzer's affection often falls madly in love with him, making the inevitable breakup infinitely worse

To be clear, he is not a cheater, and he sees himself as having very strong relationship morals/etiquette. Girls he dates might disagree and often characterize a hozzer as an asshole, douchebag, or life-ruiner. Everyone is at risk with a hozzer, hozzers are non-discriminate in their choices and have even been known to go after close friends.

Also: to hozz, hozzing, and hozzer-ish