Maxperson
Morkus from Orkus
Let me see if I can kill you in one hit with a longsword. There's no way my strength is 18, so even on a crit I can't do 20 points.
If you live, I'll accept your claim.
Nope. That doesn't work. Hit points are also a measure of skill, luck, divine protection, etc. That means that when you swing, if he dives out of the way and you just barely nick him physically, it could still be a 16 point crit.