After my initial reaction that Ollie should have killed Slade, and revisiting the words he said to him in the cell, I've come to understand that by not killing him he had proven to himself he's graduated to the level of a super-hero who fights crime but does it without (purposely) killing the evil-doers. Like Batman!
BTW, I posted this in the new thread about the Flash on CW
"Over on CBS sibling The CW, the network looks to have what may be the most likely success among all new broadcast series next fall in “The Flash.” The CW did an excellent job of launching this show, first by making it a backdoor pilot out of “Arrow,” and then by giving it one of the splashiest introductions in all of upfront week at the network’s high-energy event. “The Flash” strikes me as a show with the potential not only to succeed but to cast a halo effect over its entire network, the way “Gossip Girl” once did."