Secret Agent Sayid
By the mid-point of the series, Lost was a narrative melting pot, incorporating aspects of practically every major genre. The weekly flashback-per-character structure had lent the show a 31 flavors-vibe since the beginning, but around season four/season five, all of these elements came to the forefront, creating an atmosphere that could simultaneously blend action and adventure with a sweeping, Notebook type romance story and a scare-filled horror cabin to boot.
But the mixture wasn't always stable. In retrospect especially, some elements feel grossly out of place. Many fans felt jerked around when the show introduced time travel, and while that arc did have its problems, at least it was hinted at earlier and then significantly impacted the overarching story later. No, our biggest nitpick isn't time travel. It's Sayid's between island assassin tour, for no other reason than how ridiculously vague it was.
We got a great self-contained episode in "The Economist," and then what exactly? For several Sayid-centric hours we watched him vengefully jaunt around the globe, executing faceless suits that Ben, and the show, informed us were somehow important to Charles Widmore and therefore dangerous to the castaways, those that escaped and those still on the Island. But we never learned anything more about these people, the danger they posed, who the eponymous economist was, and, on top of that, Charles Widmore ultimately flipped sides.
All this subplot boiled down to was, Sayid is best with a gun in his hand and Ben is best when he's being shady and manipulative. So Darlton gave them a vehicle to exhibit their best qualities until they returned to the jungle. At the very least, they could've choreographed better action sequences than this. Knives facing up in the dishwasher, who does that?