How much damage can an 18th lvl fighter reliably do in a round?
I don't have the PHB II, but here goes. Feel free to comment on his equipment choices. I will try to be conservative but well-tuned.
I'm assuming an enemy AC of 35 or so. He has +18 BAB, a Str effectively of around 24 or so (+6), a +4 flaming burst longsword, and numerous feats, including weapon focus (longsword) and weapon specialization (longsword). His to hit is around +30 or so before buffs. Assuming he takes -5 to hit with a power attack, his damage is 1d10+17+1d6 (avg 28), and on a crit, 1d10+34+1d6+1d10 (avg 48.5). With Improved critical, his threat range is 17-20, or 20% of his rolls. I'm going to assume he confirms, either because of Power Critical or oil of bless weapon or somesuch.
His first attack is about even odds to hit, his second has about one in four, and his third and fourth hit only on a 20 but always threaten. So his main attack averages 14 damage, with even odds to threaten, so average 21 points. His next attack is about half that, so we're at 30 points. His remaining attacks add just about five each on average.
So for a relatively vanilla longsword specialist fighting one-handed, we're looking at nearly 40 points a round of damage per full attack. Using a two-handed weapon could likely take that through the roof.
It would appear to me that +100 damage wins, but only just.