Daniels, played by Matt Winston, was a Temporal Cold War operative from the future. That may sound cool, but his entire character arc was centered around convincing Jonathan Archer to fight a time-war from his time and providing him with information on how to do it. A war that Archer may have in fact started.
Daniels was fine but the big issue with Daniels, besides the lack of depth given to his character, was that his storyline is easily the worst part of the show.
The Temporal Cold War arc was both obsessed over and not developed enough, popping up randomly, like a side quest in a video game. It was how the series launched, with Enterprise having to deal with the mysterious future man’s associates, the Suliban. The Suliban ranked right up there with the Ferengi among the worst villains Star Trek has ever created. They were just sucky lizard ninjas.
Somehow, despite the Temporal Cold War being one of the least popular ideas that Star Trek ever created, the show never gave up on the concept and in turn Daniels. The character appeared eight times in the series, across all four seasons. One of only a handful of characters to appear in a recurring role in every season of Enterprise.
Thankfully, it did help get us to the Storm Front two-parter in season four, a pair of episodes that are underrated in the history of Enterprise, if not Star Trek as a whole. That was, however, the only saving grace of Daniels and his nonsense.