Arrow Season 5 went out with a bang... literally.
The final episode of the fifth season - which saw the show make a big return to form - had Adrian Chase bring everyone Oliver cares about to Lian Yu, with the threat of either killing all of them, or his son William instead.
Oliver, with the help of some old friends/enemies - including Slade Wilson, Digger Harkness, Nyssa al Ghul, and Malcolm Merlyn - attempted to stop him, opposed by Chase, Black Siren, Evelyn Sharp, and Talia al Ghul.
It resulted in a truly explosive finale, with Arrow delivering an all-time great episode of the series. It brought the flashbacks full circle, with the rather emotional return of Moira Queen to boot, and brought to an end the twin Big Bads of the seasons, Kovar and Prometheus.
It also, maybe, killed off just about everyone apart from Oliver and his son. In a fitting way to bring this chapter to a close, Lian Yu was destroyed, but all of Ollie's friends were on it. No doubt the show will find some way of rescuing them, but there will also - surely - be at least a couple of major casualties when the show returns in October.