To maximize mele damage first you're going to need the basic mele skills
berzerker, pumping iron, frenzy (optional to get berzerker buff), Bloodthirst, crits (optional if you want to deal a stupid amount of mele damage), etc.

Next you need the infiltrator perk deck because of the skill called overdog which says if you hit an enemy within 1 second of hitting another enemy that enemy will take 10 X more mele damage. upon researching and testing (with wolfhud) i have found that the mele effects lasts for around 5 seconds and not 1 so there's 5 seconds for you to charge your mele weapon fully


now the last two things you need are any high damage mele weapon such as the katana, (optionally crits if you're that determined to go beyond the health limits), and bloodthirst stacks

Now that you have all those skills. lets do the math bloodthirst (as we know) says it can stack 16 times. by testing with wolfud it stacked only 15 timesso with that because I was getting buffed by berserker and other skills. my mele dealt around 31X more damage. after hitting an enmy with the equipped skills (berzerker pumping, iron, etc.) and by using wolfhud i found that the overdog skill increases your mele damage by 21X after hitting an enemy with the skills equipped which means if you get full bloodthist stacks and hit something with your mele you will be able to deal a total of 351 X base mele damage combined with the already buffed katana damage you will deal a stagering 49140 damage (and 147420 with crits) Not only that if you have a fully charged mele you can deal up to 315900 damage (and 947700 with crits) when fully charged

So now you know how to get the maximum damage and the skills you need, so how to do it? first you need to get all bloodthirst stacks (15 or 16 kills idk i'm lazy) to multiply the mele damage by 31 X. next you will need to mele your AI teamate to activate overdog (and yes i have tested it and meleing your own AI teamates WILL give you the overdog buff although i am unsure if this works with players) to multiply the damage buff to 351 X next find the nearest enemy and kill them with one hit

this instantly kills ANY enemy in one hit on any difficulty. Crits are unnecessary and charging the mele is also unnecessary as the damage will already be enough to oneshot anything unless you can mele the SWAT turrets, <(which i havent tested yet) crits and mele charges are unnecessary.

Video on how to do it
(I did it on normal cuz i'm lazy :p)


Notice the buffs and the mele damage increace which is marked by +M Dmg