(chuckles again)
My powerful character attacks with his Destruction spell from 1st Edition.
No saving throw, and his assault will batter through Spell Resistance.
The poor opponent - that ONE opponent - dies.
My character has now thrown his one allowed spell per round, and his action is over for the round.
It is the opponent's turn.
10, or 20, or 57 spells come at my character, all at once.
Plus spells dropped into a Time Stop, then unleashed. Plus spells from the Simbul's Spell Supremacy and Mantle Spells, plus God knows how many Quickened spells.
Plus spells from multiple heads.
Plus spells from the Two-Mind spell.
Hmmm ... and of course, all the incomings are Maximized, Enlarged, have + 20 or better to pierce all SR and all Saves, are Doubled, Chained, Repeating, and Heaven knows what else.
Can we say Sub-Atomic Particles?
And THAT doesn't take into account incoming Epic Spells, or Epic modifications to the normal spells to produce 300 hit dice Fireballs (Maximized, of course) ...