This would be more formal grammar: "He's
thatthe kind of friend that /whostays with you till the end." I think who would be more common in conversational AmE.
"I remember when all (of) the people were hating (on) me." Hating on me is current in AmE slang. The first bit is OK with or without of. A more natural sentence might be I remember when everybody was hating on me.
Student or Learner