A 12th level fighter will chop multiple ogres to bits in one round.
I feel this claim has already been refuted multiple times. But here's another go around.
In AD&D, a 12th level fighter has 3/2 attacks per round (PHB) or 2/1 attacks per round with a specialised weapon (UA).
If using a longsword, damage per hit vs an ogre is d12 +6 (a fighter at that level probably has Gauntlets or a Girdle or some other way of getting buffed STR) +3 (a reasonable weapon bonus for a fighter of that level, having regard to published modules, the NPCs-in-dungeons treasure tables, etc) = average 15.5. An Ogre in AD&D is AC 5 (so auto-hit unless the table uses a miss-on-a-1 rule) and 4+1 HD, so a single hit has a meaningful but certainly not guaranteed chance to kill. Obviously weapon specialisation increases that chance.
If using a two-handed sword, damage per hit is 3d6 + 6 + 3 = average 19.5. The chance to kill is good.
So this fighter is able to kill an Ogre a round pretty reliably.
The fighter's hp are, say, 68 (+2 CON bonus), and AC is probably -2 (plate mail +3, DEX +1, +1 sundry) or -5 if using a shield (shield +2), so an Ogre hits on a 17 or a 20, for d10 damage or weapon +2 damage (GM's choice). The sword and shield fighter can withstand (on average) around 200 Ogre rolls to hit. The two-handed sword fighter is more vulnerable, because of the statistical quirk on the attack table - every additional point of AC they can eke out helps them tremendously whereas it makes no difference to the shield-wielding fighter (unless they get their AC below -10 and the GM decides that makes them untouchable).
If we assume two Ogres can attack per round (eg the fighter has their back to a wall/corner - this also means we don't need to factor in any Ogres having a positional bonus to hit), the sword and shield fighter can survive up to 100 rounds. And so can withstand a horde of 50+ Ogres. At about 200 XP per Ogre, that will earn the fighter 10,000+ XP, or one twenty-fifth of a level.
For comparison, a fireball from a wizard with the same number of XP - 1,000,000-ish, so a 12th or 13th level wizard - does base 42 or 45.5 damage (12 or 13d6) so will tend to kill every Ogre in its radius (an Ogre's save vs spells is 14, or about 1 in 3; so fewer than 1 in 6 ogres will survive the fireball).
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In 5e D&D, the 12th level fighter has +4 to hit (level) +5 (20 STR) + sundries (magic weapon, other buffs) and so will tend to auto-hit an Ogre, though perhaps not quite if using a -5 to hit feat. Damage with a longsword will be d8 +5 (STR) +2 (style) +3 (sundries) = average 14.5. That's around 4 attacks to drop an Ogre. So even with Action Surge it's unlikely that multiple Ogres will be killed in a round.
With a greatsword, damage is 2d6 +5 (STR) + 1 (style, rounding down very slightly) +10 (feat) +3 (sundries) = 26. That's just a bit over 2 attacks to drop an Ogre. With Action Surge it's likely that two Ogres will be killed.
If the fighter is a battle master, they have 4d10 of superiority dice. That's another half-Ogre or so.
If the fighter has +3 plate armour, their AC is (say) 22 (including +1 sundries) or 24 with a shield. The Ogre has +6 to hit for 13 damage, so hits on a 16 or 18 for an expected damage of 3-ish or 2-ish (again, the statistical quirk makes having a shield pretty good, though not as good as in AD&D). The fighter has 112 hp (CON 16) + 18 from second wind (rounding up) so 130. So can withstand 40 to 60+ Ogre attacks.
Unlike AD&D, the greatsword fighter is better here: assuming two Ogre attacks per round, they can defeat an incoming horde of around 30 Ogres. The 13500 XP are more than half of what is required for the next level.
For comparison, a fireball from a 12th level wizard can do 8d6 to 11d6 (6th level slot). It has virtually no chance of killing an Ogre, though it can give one a nasty burn.
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My conclusion: it's an exaggeration to say that a 12th level fighter, in 5e D&D, will chop multiple ogres to bits in one round. They
might do this with Action Surge. When compared to AD&D, the 12th level fighter is weaker vs Ogres, but not hugely so: the difference between a horde of dozens of Ogres and a horde of hundreds is probably not that much in most narrative contexts.
The 12th level MU, on the other hand, is not as good at mopping up Ogres with fireballs in 5e as in AD&D. This seems generally consistent with the change in emphasis, certainly there in 3E, on what counts as good wizard play: from artillery to control.
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Werewolf addendum: in AD&D a Werewolf has AC5, 4+3 HD, and does 2d4 damage on a hit. So is largely interchangeable with an Ogre in the above calculations, though is worth about 300 XP (because their immunity to ordinary weapons and their diseased bite give them an XP step-up).
In 5e, the Werewolf has 58 hp (compared to the Ogre's 59), but only +4 to hit for 13 damage (hybrid multi-attack). So the 5e fighter definitely prefers to face a pack of Werewolves to a horde of Ogres, especially as they're also worth 700 XP each!
