Lanefan
Victoria Rules
You're forgetting UA's weapon specialization, which is going to give +3 to damage and (depending on level) faster attack rates.I'm a bit confused as to how a fighter could kill a giant in one blow. <pulls out 1e stuff>
OK, let's assume a completely average hill giant (HD 8 + 1-2--I'm assuming that means 8 HD + 1-2 hp, not 8 HD + 1-2 HD; it's just written weirdly), so... 37 hit points.
Let's also assume a fighter with 18/100 Strength, who does +6 damage, wielding a bastard sword +5 (2d8 damage). So... a maximum of 27 damage per round.
Also, there were specific weapons designed for giant-slaying which did double damage against them. And a two-handed sword does 3d6 against Large, so I make the max. 18 + 3 (spec.) + 6 (strength) + weapon (2-h. swords go to +3 if memory serves); and if that thing's a giant-slayer, double it all.

Yeah, there's a reason I beefed up Giant hit points a very long time ago.

Not by RAW but there may have been a very minor system introduced in an early Dragon - something like double damage on 5-6/d6 on a nat. 20.Which rather suggests that it's only possible to kill a very weak, below-average hill giant in one blow, if your Strength and weapon are both maxed to the gills and you roll max damage. Were critical hits even a thing in RAW 1e?
A lot of 1e's major monsters really were glass cannons. Dragons are the poster child.It's just not much to brag about how powerful fighters are if you're killing the hill giant equivalent of a 98-pound weakling.
The bright side is that combats were always short.

Nope, 1e fireballs also expanded to fill the volume of that 20' radius sphere; which worked out to about 33 10x10 cubes. (very useful when using 10-wide x 10-high passages and rooms with 10'-high ceilings!)Especially since a 5th-level wizard could fireball that giant for a max of 30 damage in a... 2" sphere, whatever that meant in 1e; I've forgotten (huh; I guess it was 2e that introduced the dungeon-cleaner fireballs.)