I think his greatest strength feat is carrying around and throwing a gaint bomb-omb.
His respect thread puts him at class 100 in his greatest portrayals.
Just checking as nobody for 10 pages could be bothered to post the link.. wait, 6 times in 4 months.... *ahem* moving on.
Reason I say its a gag:
YouTube video
At 1:45 is the only knows castle throw I could find, though it look more like he kicked or humped it away.. note how the castle is inside the castle which is itself (inception D: ) and how Mario reacts to it as if it were only twice his height.
Anyways 0:41, 1:00 and most importantly 1:25. The methods of destroying the castle are only flashy gimmicks and not something that are canon to Mario's abilities.
These scenes aren't legit showcasing of what Mario can do.
We to deh tango now?
With rule 14; Mario throws a castle, but how big is this castle? Well it happens to be twice the size of Mario. You can hide behind the rule and end up with an unquantifiable feat thats only measure is that it top is reachable with a stick, or admit that its not a legitimate feat.