Um, this episode was a little strange. It wasn't bad. It just felt like we were watching a Saw/Dexter mashup of a show instead of Arrow.
So, while Chase has Oliver locked up and is torturing him, we get a bunch of Russian flashbacks. Where Anatoly says similar things to Oliver that Chase is saying.
But, in the present, Chase is desperate for Oliver to tell him his secret. The thing that's so dark he can't admit it to Felicity, Diggle, or himself. For most of the episode, Oliver claims he has no idea what it is.
In the middle of this badgering, he throws Evelyn in the cage with him and tells them to kill each other. And whoever is left standing, he'll let leave. Evelyn tells him that she was wrong to go with him and that she's sorry. Oliver forgives her, but tells her to give him the knife. She tries to attack him with it, but he pushes her away. Eventually, Chase comes back, sees that neither of them is dead and 'snaps' Evelyn's neck.
He goes back to badgering Oliver about his secret. Eventually, pulling out of him that he killed all the people because he wanted to and he enjoyed it. Oh, and here's where we find out that Evelyn is actually alive and still on Team Prometheus.
This sort of seemed like it came out of nowhere. I thought maybe he was just telling him what he wanted to hear, but immediately after he was freed, he limped his way back to the Arrow cave and told them that he wasn't doing this anymore. He no longer wants to be the Green Arrow.
Also, after he admits this secret to Chase, Chase decides it'd be super fun to burn off his Bratva tattoo. I don't know exactly what they was about. It seems like there is a deeper meaning to that.
Either way, there are, like, three more seasons, so I'm sure Team Arrow is over, but I don't know what happens now.