The Flash: Ranking Every Character From Worst To Best
23. Hartley Rathaway
A scorned colleague of Cisco and Caitlin, Hartley Rathaway sought to gain vengeance on Wells for mistreating him and, in doing so, became the villain known as the Pied Piper. However, an unexpected heart-to-heart with Cisco primed him for an involuntary redemption - which came to be after Barry accidentally messed with the timeline and, in the process, turned him into an ally.
The character was well-developed in a rather short space of time, and actor Andy Mientus had great chemistry with all of the S.T.A.R. Labs team, so it goes without saying that Hartley would make a great full-time addition to the show - and, quite frankly, it's baffling that he hasn't appeared since Season 2.
He may have only appeared in three episodes, but his importance lies in the fact that he was the only character to see through Harrison Wells/Eobard Thawne long before anyone else ever did and, more than that, his unexpected redemption was a shining example of the adverse effect of timeline manipulation.