It's the opposite of a eulogy. Instead of speaking of a dead person's better qualities and praising them for their life achievements, a fuckeulogy focuses on the dark side of the dead person and all the misdeeds they have done. Fuckeulogies are reserved for those who are universally hated by the masses, and who will in no way, shape or form be missed when they die. It boils down to delivering the final 'fuck you' to a dead person at their funeral.
People who would qualify: Hitler, Mussolini, Stalin, Saddam Hussein, Gadaffi, Kim Jung Il, Osama Bin Ladin, etc.
The term was coined by satirist and comedian John Oliver (seen on 'The Daily Show' with Jon Stewart). Oliver coined the term on his Podcast 'The Bugle' with Andy Zaltzman (episode 152).
Dumping Osama Bin Laden's body into the sea robbed the survivors of the 9/11 dead of delivering a decent fuckeulogy.