The Collaborative International Dictionary of English v.0.48:
Ruiner \Ru"in*er\, n. One who, or that which, ruins. [1913 Webster]WordNet (r) 3.0 (2006):
ruiner n 1: a person who destroys or ruins or lays waste to; "a destroyer of the environment"; "jealousy was his undoer"; "uprooters of gravestones" [syn: destroyer, ruiner, undoer, waster, uprooter]