My fireproof blanket burned and I had no ring of ice in ToEF. I was lucky enough to get acidic blood corruption which helped me making ACW blind several times in melee and once while it was blind I was able to stab it to death. Then:

You exactly hit the titan and critically injure him. The * quarrel of giant
slaying (+3, 2d8+3) is smashed! The titan hits you. The titan is
splattered with your acidic blood! The titan is dissolved! [+138278xp]