I would like to note that the warrior caste (little known fact: Klingons were once a caste system and that system is still "alive" when Trek rolls around, but it is just moderately adhered to) are significantly stronger than the rest of Klingons. Those are usually the ones seen in any military actions/campaigns. Those are the warriors. Worf comes from this group. Worf is among the strongest if not the strongest of the Klingons because he, time and time again, showed he was a better warrior against their best.
Here are a list of strength and battle feats from Worf:
1. Besting the cloned Kahless (who would obviously have a natural genetic predisposition towards being the ultimate warrior as he united the Klingon warriors and proved himself, over and over, in battle, as the best Klingon warrior of his time) who was trained to be an indisputable warrior. This same Kahless defeated a challenger earlier in this 2-part episode but Worf pwned him. 🙂
2. He picked up a man, with one arm, with his arm extended, by that man's throat or that man's shirt. Can't remember which. But that's well beyond what any human, no matter how strong, is capable of doing.
3. As Robtard pointed out, he fought against a genetically engineered group of warriors and bested them all until his injuries and lack of decent food and water caught up with him. The Jem'Hadar, even as adolescents, were more than a match for even a well-experienced Starfleet security team. It was stated that the Jem'Hadar have multiple times the strength of humans. Worf dominated dozens of them over the course of 3 days until the best of their group, their First (title of the leader/alpha male of a platoon), fought a badly injured Worf. Worf's fights lasted hours, each, because the second day, he only fought and killed 2. Worf has massive endurance as he fought, literally, all day. Keep in mind, he's still besting them by the end of the second day with little food and water once he gets back to his cell. He also has broken ribs and other injuries (concussion). So he is at least stronger than some of the fiercest Jem'Hadar warriors as these Jem'Hadar are assigned to a Dominion prison.
A weakened Worf is stronger and has more indurance than some of the strongest Jem'Hadar.
Worf>Jem'Hadar>>>humans. This is based on onscreen evidence: no extrapolation required.
4. Worf bested Gowron, the Klingon Chancellor, in ritual combat. Before anyone dismisses this, Gowron maintained his position as Chancellor bey defeating many challengers, in ritual combat (to Picard's disgust), to the death. Gowron is a fierce Klingon warrior and among the best if he was able to defend his position during the tumultuous times that almost lead to Klingon civil war.
So it should be clear that Worf is not the typical Klingon. He's not just barely stronger than a human, as many other Klingons clearly are. He's stronger and more skilled than any Klingon we have seen: even a cloned Kahless. He's stronger and more skilled than the Jem'Hadar who are multiple times the strength of humans. The estimate on this website says that 1 in 625 males (age 17-59) regularly weight train to the point of being able to hit a 300lbs bench press. The rest, the majority will bench between 130-160 lbs at their peak. You know what that means? The superhuman, Khan, is only 2x as strong as I am. 😄 Worf is definitely definitely definitely stronger than I am. I find his picking up a man with one arm, fully extended, to be a better strength feat than anything Khan did...mostly because with double my strength, I still could not do that. I might be able to do it with two arms, but not one (with double my current strength).
So much for Khan's superhuman strength being a deciding factor in this fight, eh? 😄