Arapaima can exceed 6ft. Heck, some have been reported to reach 3 metres and above. Goonch catfish are pretty terrifying and there have been numerous reports of them killing humans
Not sure if anything can take down a Wels. I have two, and the only thing that has bothered them, ever, is each other.
But, they don't bother other fish.
You can't really debunk these, because lots of these don't even occur together in nature.
The tiger fish caught by Wade died shortly after capture - how about that for a debunk?