Solomon Grundy
The Solomon Grundy developments seem to be lifted directly from the comics. Jade got him in a no win situation trying to stop a glacier avalanche. She promised to take him somewhere warm if he helped even though he swore to kill her. She kept her word and in his mind that made her his friend.
Same thing is happening here with Rick. He let Grundy live so now he is his friend.
I'm just hoping it doesn't resolve itself the same way it did in the comic books.