Manga isn't exactly canon, same with Hyrule Warriors.
I get it sucks to admit, but both Cloud and Sora are stronger than Link, composite or not. Link is really strong, but Sora has been shown to be able to cut through buildings with a single swing. If Link used his super strength you claim he has to throw a 10,000 ton pillar, Sora could cut it clean in two.
Here's the thing though. Link doesn't have to.
Over the course of the Zelda Series, there has never been a hit that Link could not block with proper timing. He can simply absorb any hit that came at him.
**** it. As a child, this little badass completely absorbed hits from giant falling volcano debris with just a Hylian shield on his back. So Sora would just not be able to hurt link in his prime.
There is absolutely no way Link would touch Cloud in his prime. Wouldn't even be close. Cloud survives this:
Dude would straight up shred Link into pieces in his sleep.
Also, that death battle crap is garbage, Masterchief beating Doom guy? LOL!!!! What a joke! Doom guy single handedly destroyed all of hell by himself. Just a little tidbit.
You are forgetting that Death Battle didn't even show Link at his finest either. I mean, Link has items that literally make him untouchable. Goron Link would crush cloud. Fierce Diety it would not even be a fair fight. Zora Link can easily simply drown cloud if he was near the water.
Link also has an item that not only makes him invincible, but also does a ton of damage.
Here's the kicker though. At full strength, if Link somehow was close to losing. He could just go back from time and retry, simply warp out of the fight.
Link has also proven that he is way more versatile than Cloud. Link has many strategies that Cloud simply has not. Cloud just wacks stuff. Link forms a strategy to take care of any enemy and exploit his enemy's weak points. Cloud has never done this, nor will he ever. This in itself gives Link an even bigger edge than before.
Not to mention Cloud clearly has better hand eye coordination and weight distribution considering he can balance the Buster Sword in battle one handed like a champ, but Link must start his swing with the Biggoron's Sword two handed so he can better distribute the weight, leaving him at a disadvantage.
Why would Link ever want to use a big sword against Cloud?
Link is all about defense. Link can quite literally block all of Cloud's attacks, while Cloud gets hit by attacks 95% of the time in FFVll. Cloud has no respect for defense. But that is his downfall.