How to get rid of Watermarks?

This is timely for me as i've been trying to this myself with some of the episodes from the rare and obscure TV series uploaded by Youtuber Rare Gems, unfortunately he's started watermarking some of his videos now(in what I presume is an attempt to avoid copyright as he's had his channel taken down twice before)fortunately for some of his shows like Nick Freno Licensed Teacher I was able to find non-watermarked rips from his old channels on Internet Archive, hopefully the same will be true for his other uploads. So far all the software i've used to try and remove watermarks ends up leaving an ugly blur behind(which actually results in part of the opening credits getting erased)which is unfortunate.