Lets talk about Letho (contains The Witcher 2 & 3 spoilers)

Personally I think that Letho is one of the best frienemies of any fiction, and one of the best contributions which the witcher games had to the series.

Here we have a guy who's repeatedly taken as the fool, only to be the one prevailing in the end more-often-than not. Despite looking stupid, everyone who tries to take him for the fool usually ends up outwitted (the "Smarter Than You Look" trope occurs more than once in the witcher series, the other notable instance being with Sigmund Dijkstra). In fact, as far as I know, throughout the series nobody ever is able to really get the better of him. Sure, he gets used by Emhyr, but he gets away with his life, which is better than most of Emhyrs enemies can say. To further this point, if Geralt does end up killing Letho it's because Letho chose to wait up and more-or-less say "I figured I'd give you the chance to try to kill me, if you want." In my playthrough of The Witcher 2 I chose not to kill him, because given what the guy said, what's the point? With that in the past, I loved Letho's appearance in The Witcher 3-- which really concreted his status as frienemy of the century for me.

I'd like to know what you guys think of this character. Are his actions forgivable? Is he a cool-dude or an utter tool-bag? Am I giving him too much credit? How about his writing, do I think too much of it-- and he's actually a stale or generic character?