Oz killing Vic was meant to show he’s an irredeemable piece of shyt. Vic was naive and in his naivety he believed Oz loved him and was family. Everything his mom said in the club was true and the price he pays is knowing the last thing his mother did was try to kill him. He’ll never hear her say she’s proud of him, he has to settle for ole girl portraying her which in and of itself is sick because he bangs her. The final moments of the episode were meant to hammer home that Oswald is broken, delusional and insane.