I choose a strong punch to the upper torso, which is instantly fatal to the sort of feeble chump who only has 4 Hit Points in spite of starting with maximum HP at first level, and of which a heavyweight champion can shrug off dozens before falling unconscious.
Heh. Harry Houdini would like to have a word with you.
The laughable thing is, you're still arguing that the game world is based on some sort of natural processes - some sort of internal logic and not completely subjective ideas dreamed up by the DM. The fact that the DMG tells the DM to basically pick his own spells to not work on other planes and gives absolutely no reasons why magic doesn't function on other planes apparently isn't subjective enough for you.
Ok. Explain this to me then. Let me set up the stats for you. This is from the 3.5 SRD, although, IIRC, the physical stats for these monsters, relative to each other, haven't really changed much between editions.
Ogre: 9-10 feet tall, 600 (ish) pounds, Str: 21 Con: 15 HP: 29 CR 3
Bugbear: 7 feet tall, 300 (ish) pounds, Str: 15 Con: 13 HP: 16 CR 2
Troll: 9 feet tall, 500 pounds, Str: 23 Con: 23 HP: 63 CR 5
Hill Giant: 10 1/2 feet tall, 1100 pounds Str: 25 Con: 19 HP 102 CR 7
Now, tell me again how HP is a measure of how much physical damage you can take. A hill giant isn't that much bigger than an ogre, yet has three times as many HP. A troll is actually smaller than an ogre and has more than double the HP. Our Bugbear, OTOH, isn't that much smaller than a troll, yet has a quarter of a troll's HP.
It's almost like the game designers realized that higher level characters need higher level challenges and then assigned different monsters for different character level ranges to encounter. So, you progress from ogres to hill giants as you gain levels. What a shock and surprise. Here I have been told that HP are purely a measure of physical toughness and that all things in D&D follow through some simulation process.
So, what exact in game justifications are there for two creatures of roughly the same size being wildly different in toughness? Why, exactly, does a hill giant have three times as many Hit Dice as an ogre and twice that of a troll? Why should a troll, which is considerably smaller than an ogre, have more Hit Dice than an ogre?