Chaos_Marine: Fist fighting is hilariously easy to cheese. I beat the first four fist fights before I hit level 8 without needing to block or counter much at all.
Simply move in, strong punch. Move back outside of pushing distance (about a meter or two) then push back in and use another strong attack. Yeah it's laborious and time consuming but more than easy to do.
The hardest one for me was the ex-military sniper because reasons you'll find quickly after you beat him. Just bring a lot of grenades is all I'll say.
wayke: The Cyberpyscho
Legendary - System Reset not even a fight.
If it's that one cyberpsycho that crouches behind the broken car inside that yard and starts "teleporting" using cyberware - it's actually pretty trivial to beat him, IMHO. I had 3 points in Body and 4 in Reflex, and I fought him using an uncommon electric club at around lvl10, probably less. For all his "teleporting", after he gets close to you, he always does a completely telegraphed heavy attack which lasts for *ages*. In the end I just parried and got in 4 free hits. Rinse and repeat. He always does the same heavy attack if you get far enough away from him. I do have to admit that I gave him a cyberware malfunction at the start of the fight. It didn't last until the end, though. Just parrying consistently is much easier than throwing dozens of grenades at him, in my opinion (I was killed every time I tried being smart, and I didn't want to kill him, because quest).
And yes, System Reset rules.