One of the most fascinating relationships in the DCU is the one that exists between Red Hood and the Joker. The two are bound together by the worst day in Jason Todd's life: his death. Understandably, Red Hood holds nothing but animosity for the Clown Prince of Crime, but the Joker's own feelings for Batman's second Robin have always been ambiguous. They have ranged from annoyance over his old moniker being used on the side of good, to even amusement that someone he killed hated him so much that he came back from the dead to avenge himself.
Source：https://www.cbr.com/gotham-war-red-hood-joker-relationship-touching-dc/
