It's impossible not to approach each Arrow season finale with trepidation. The Season 1 and 2 finales were both great, ranking among the show's overall best. But the Season 3 and 4 finales were the exact opposite. Arrow has developed a nasty habit of falling apart at the finish line in recent years, and even with all the improvements the show has undergone this year, there's always going to be that fear that the show will blow it in the end. Thankfully, that's not the case with Season 5. "Lian Yu" isn't just a great season finale, it's quite possible the show's best episode ever.

Arrow: "Lian Yu" Photos 24 IMAGES

The series truly came full circle this week, wrapping up Oliver Queen's five-year flashback saga and dragging him back to the island where it all started. In the process, pretty much every surviving character of note (and one dearly departed favorite) returned to help the show celebrate this important milestone. This was a jam-packed episode that managed to never lose sight of Ollie's very personal mission. It's funny to note that this is the first time the writers cooked up a finale that didn't involve Team Arrow racing against the clock to save Star city from destruction. Despite that, this episode felt as epic and eventful as any of them.What better way to kick things off than with an extended reunion scene between Ollie and Slade Wilson. Slade still and probably will always rank as Arrow's most compelling villain (though Adrian Chase made a really strong case for himself tonight), so I was thrilled to have the chance to reconnect with the character after a more than two year absence. This episode did not disappoint. Slade has clearly mellowed out since last time he clashed with Oliver. He no longer really qualifies as a villain. Freed of the effects of Mirakuru, Slade is free to rekindle that brotherly bond with Ollie that died along with Shado. One of this episode's greatest strengths was playing on that bond and reflecting the full, complicated history between the two characters.It really helped that Manu Bennett was able to free himself from his Shannara Chronicles commitment long enough to appear in the episode. I'm not sure why Bennett and Marc Guggenheim gave the impression that Bennett was only doing voice-over work for this episode. All I can think is that their recent Twitter spat was some sort of weird, manufactured PR stunt, like when pro wrestling beefs supposedly spill over into real life. Whatever the story there, it was great seeing Bennett in the flesh. It was one thing to watch the armored-up Slade hacking his way through ninjas, but his scenes with Ollie simply wouldn't have worked as well if Bennett and Stephen Amell weren't in the room together. I only wish there had been room for some direct interaction between Deathstroke and Prometheus. That might have made for a fun dynamic.Having Nick Tarabay's Captain Boomerang back was also a welcome surprise. The character wound up playing a pretty minor role in the grand scheme of things, but his banter with Ollie and Nyssa was enough on its own.This episode did drag a little bit in between the Ollie/Slade reunion and the start of the final showdown. There was a little too much of characters walking through the forest and having heartfelt conversations. But right about the point where Thea stepped on that landmine, the tension shot back up and the episode continued building momentum until the very end. Who would have expected Malcolm of all characters to be the first casualty? It does feel like it's time for the character to ride off into the sunset. And he certainly had a great death scene, saving his daughter's life one last time and taking Boomerang down with him. Though, to be fair, a faraway explosion isn't exactly definitive confirmation that a character is dead. If it were, the final cliffhanger would be even more dramatic and upsetting (more on that in a bit).The big Team Arrow/Team Prometheus showdown was certainly memorable. The choreography in the main fight scene was top-notch, with every major character pairing off and dozens of bodies in motion at once. The Black Siren/Black Canary and Nyssa/Talia fight scenes were also a lot of fun. The writers managed to find opportunities for pretty much every character to shine during this sequence, even if just for a moment or two. Again, even though there wasn't an entire city at stake in this conflict, the scope of the battle was truly epic.As all of this carnage was unfolding, we also got one final look at Ollie's feud with Konstantin Kovar. The interplay between past and present reminded me a lot of the dual-Deathstroke battles from the Season 2 finale. The actual plot of the flashback storyline this week was about as basic as it gets. Ollie wanted off the island. Kovar wanted him dead. They fought. Ollie won. He got off the island. But their final battle worked well all the same. There was a real brutality to the combat. No weapons or fancy martial arts, just two men who each wanted the other dead.The real joy with the flashbacks this week involved what came after. I felt a chill watching Ollie race to meet his boat and go through those same motions that we saw in the opening of the very first episode all those years ago. It's really fascinating to see a series take 115 episodes to deliver pay off. But even that paled to what came next, as the writers found a way to work Moira Queen back into the picture for one, brief moment. That phone call may well go down in history as the best scene in Arrow's history. Certainly among the best-acted. Stephen Amell and Susanna Thompson oozed raw emotion in that scene, really nailing the idea of a long-lost son finally making his way home. I'd hate to meet the person that can watch that scene and not get choked up.This episode really needed that happy, emotional moment to offset the crushing darkness of Ollie's final confrontation with Chase. Ollie's victory this week was incredibly bittersweet. Yes, he proved once and for all that Chase can't goad him into killing again. Ollie has become whole again. But he never quite mastered the trick of out-thinking his foe. Chase remained several steps ahead till the very end, forcing Ollie into a real Sophie's Choice moment as he had to decide between his son and his friends. There was a great sense of tension to the final scene. Here, alone at the very end, Ollie became just a desperate father with a bow and arrow trying to reason with an insane, evil mastermind.I felt a sinking feeling in the pit of my stomach when I realized just how close to the end the episode was by this point. And sure enough, the episode wrapped not with a rousing victory for Team Arrow but a huge cliffhanger. By killing himself, Chase may have just wiped out every member of Team Arrow. That's quite a place to leave viewers hanging for four months. It's hard to imagine the writers literally wiping out the show's entire supporting cast. But at the same time, it's equally hard to imagine them dropping such a huge twist and then giving every one of these characters a reprieve in Season 6. Some Team Arrow members are probably doomed, and it's really only a question of which ones.This is going to be a very long summer.