I did it, with legendary Gorilla arms, 20 body with all relevant athletics perks, only 3 perk points in brawler as left over perk points. Internal bleeding, 100% charge damage mods.
They are still rather difficult on Very Hard if you don't learn to cheese the AI.
You never want to stay close enough to them that they start their punch>kick>punch combo, because the kick is unblockable and does a metric ton of damage and tracks even if you side step for no reason.
So what you want to do is keep them staggered by doing a heavy strike to the head, immediately stepping back while charging up another heavy strike, and keep them stun locked like that. If they try to block and stagger you dodge out and kite any long winded combo they try to do.
It's very tedious, but it's all about cheesing the AI so they don't go into their stagger immune, unblockable kick combos. You have to cheese distance and keep them busy with staggers so they can't start their offensive combo chain. Most of their attacks that are not the kick combo chain can be interrupted with a heavy strike of your own.
The final fight, important that you have the Zetatech mod because it gives you doubled melee damage and increased defense/resistances.
The final fight, despite Viktor telling you to hit his abs, don't risk it, the melee aiming in this game is awful, only try to land abdominal strikes when he's knocked down kneeling or on the floor. Otherwise keep aiming to stagger him with heavy strikes and backing out so he desn't combo you.
The final fight, he actually heals back up to full health when he hits about 30% HP, so you have to be really patient, toward the end he'l also start zipping around in ultra speed if you try to swing too much, so just wait out for your opportunity to stagger him with a heavy strike and then keep stunlocking him until he's knocked down, then deliver a flurry of light strikes, trying to hit his ribs/abs if you can while he's down.
Of note for all fights, well timed parries work GREAT, if you're good about blocking at the right time and doing a parry that staggers them out, fights become much easier.
They're very frustrating fights in general because they seem to completely ignore your armor and it's all about cheesing the AI.
Doesn't help CDPR was abjectly incompetent/negligent and thought that not letting you bind a key for dodges and forcing you to double tap directionals was a good idea. So dumb...