ANGEL
'liam' was born in  1727 and while out drinking one night encounted Darla who vamped him. He was then christened Angelus the demon with the face of an angel. Angelus was pure evil, he was the maker of dru (maker of spike) , he stalked her and killed her family then killed her.
In 1896 Angelus was cursed by Gypsys who gave him back his soul sending him on a life long guilt trip. It was in the 90's that the new good Angel was introduced to the slayer. As well as being a useful ade to the scoobies Angel  came very close to Buffy and eventually they fell in love. On buffys 17th birthday they made love and Angel had a moment of true happyness, his curse was removed and Angelus came back reaking havock on Buffy and her friends. He opened a portal that would suck the whole world into hell. the only way to stop it was to send Angelus himself to hell. Just as buffy faced her worse fears and killed angelus witch Willow re-enstored his soul.
Angel was rejected in hell and came back suffering severe torment. Buffy nursed him back to health.
Angel soon realised that he could not stay in sunnydale and moved to L.A . Here he met Doyle who encouraged him along with Cordelia to set up Angel Investigations his company which saves people in need!