I'm not sure what you mean. I thought that your first post asked for a script that destroyed everything near a certain object.
The trigger idea will kill units, if you want something to destroy everything (including houses) the only thing that I can think of would be a whole mess of camCreated laserguided bombs. They will flatten anything, but of course they will create smoke, sound etc while they do it. Not sure if this is wwhat you want . . . :-\
If you REALLY want to go big time then check out the tac nuke script. It uses all of the above ideas - a quick whiteout titlecut and a bunch of drop particles to create flash and smoke, a box of LGB's to create killing andand mayhem and finally three triggers to crate damage to units out to 800m in increments 20%, 50% and 100%. CHeck it out - nothing beats watching a tac nuke go off at sun set over Montignac !
Cheers
roni