Talk about someone who just won't give up. Is there a day that goes by in Starling City where Malcolm Merlyn isn't hell-bent on trying to destroy Oliver Queen? Even though he appears to have sent Oliver off to his death once and for all, he's still around, causing trouble for everyone else. He's clearly learned a lot from his DC Comics counterpart, Merlyn the Dark Archer, and the character we see on Arrow shares a lot of similarities with him — right down to being the arch-enemy of Oliver.
From the very beginning of the comics, Merlyn and Oliver butted heads, because there can only be one archer supreme in Starling City. Oliver actually took up archery because of an archer he had heard of, "Merlyn the Magician," and Arrow references this, because the Malcolm Merlyn we love to hate has been dubbed "The Magician" by the League of Assassins.
Merlyn laid low in the comics for a very long time, and resurfaced after joining the League. The League contracted him to kill Batman, and he was well on his way to succeeding until he was stopped by Green Arrow. Having unsuccessfully completed his assigned task of killing Batman, Merlyn knew he couldn't return back to the League. At this point, he basically became a freelance archer/assassin, and continued to torment Oliver this way. Merlyn even went so far as to disrupt Oliver and Laurel Lance's wedding day. Not cool, Dark Archer.
Merlyn was actually captured by Cupid at one point — and the fact that she keeps popping up makes me think that her time on Arrow isn't done yet. Anyway, Cupid captured Merlyn, and brought him to Oliver as a really twisted gift. She planned to kill Merlyn right in front of Oliver, and actually managed to slash his throat before Oliver could stop her. And since Oliver has always been a stand-up guy, he got medical attention for Merlyn, but it was too late for his vocal cords, which Cupid had cut — Merlyn is now without a voice forever.
When DC launched their New 52 reboot of the comics, parts of Merlyn now became Tommy Merlyn, and Tommy Merlyn became Oliver's best friend — this is part of what we've already seen on Arrow. But everything else about the New 52 Merlyn and the Tommy Merlyn we know is completely different. For starters, comic Tommy ends up in a coma and wakes up a year later. Probably safe to assume that's not the same path that Arrow is taking.
Image: Cate Cameron/The CW