The point at which you are so very, drunk/fucked that you Chunder, but not so very, very drunk that you are paralytic i.e. cannot talk. Therefore chunderfucked as opposed to actually fucked, totally trashed or absolutely wankered.
'Darling, I was so utterly Chunderfucked last night'
'Would you take a look at that, Darling? That girl is absolutely chunderfucked!!'
Chunderfucked is a term in rafting used to describe getting violently thrashed by hydraulic action of the river, oftentimes the victim might be recirculated or even pushed into rocks and rafts.
Some choch threw a stroke in on reptar and we hitgodzilla sideways and flipped and one of my custies got chunderfucked