When somebody adds "Fact" to the end of their sentence, they are usually stating a controversial opinion, as if the addition of the word makes it so just because they said so.
Usually it is a sign of unwarranted self-importance.
Idiot: Megadeth are dead after Rust in Peace. Fact.
Sane person: No, that's just your opinion.
# a piece of information about circumstances that exist or events that have occurred; "first you must collect all the facts of the case"
# a statement or assertion of verified information about something that is the case or has happened; "he supported his argument with an impressive array of facts"
# an event known to have happened or something known to have existed; "your fears have no basis in fact"; "how much of the story is fact and how much fiction is hard to tell"
# a concept whose truth can be proved; "scientific hypotheses are not facts"