Arrow: 10 Mistakes It Must Fix In Season 5
2. Magic And Mysticism
Damien Darhk was the highlight of Season 4. That, however, is mostly down to Neal McDonough's performance. Whatever flaws the character had, McDonough covered them up with a performance that was consistently captivating and menacing, with endless charisma, and he was missed anytime he didn't appear.
What didn't really work as well, though, and let the character down, was the 'magic and mysticism' angle they attempted this season. While The Flash (and now Legends and Supergirl) mean that supernatural elements have to be incorporated into the show, it doesn't gel particularly well with Arrow's style. That made its presence in Season 4 rather jarring, though there was also an issue with how ill-explained it all was.
There was some sort of idol, and then Oliver got a tattoo of Constantine, and then the idol appeared in present day, and Darhk was suddenly ridiculously powerful and feeding off souls, but Oliver could fight him with lightness, meanwhile thousands of people were killed by nukes but no one really cared. Arrow needs to dip a toe into those waters occasionally, because of the existence of metahumans, but it's not capable of handling it for a full season, and needs to be more grounded going forward.