my actual real reason and number one character is caesar
because up until fortification hill, you're literally spoonfed stories from the ncr about how the legion is a hoard of absolute evil, even witnessing the carnage at nipton yourself and all this hatred and animosity builds and builds up until the moment where you actually meet caesar and
he makes some very compelling arguments for his rational regarding the legion
it's one of the moments in the main quest arc that truly utilizes the karma system to its fullest
edit: i also love ulysses - the whole lonesome road dlc was such an atmospheric trip tbh
btw most evil character in the whole game is quite arguably jean-baptiste imo
on a non serious note tho
fisto, mr fantastic, mean sonofabitch, tabitha, no bark noonan, yes man
all of them are comically brilliant XDD