Attack that deals more damage the closer you are to the target?

[Skullruss]

Looking for an attack that deals more damage when I'm really close, kinda like a shotgun. The idea is based mostly on Andrew Jackson's dueling, where he would tank a shot, walk up, and end the duel. I want to do something very similar: force enemy into a 1v1 (got that part already with a spell I found), then deal an absurd amount of upfront damage when I walk up. Preferably this would be a ranged weapon of some kind, but spells are cool too.

[Bronk]

You could use iajutsu focus at short range by drawing a dagger (melee weapon that doubles as a thrown weapon), then throwing the dagger. Also, any form of ranged sneak attack.

[Gruftzwerg]

An Assassin (https://www.d20srd.org/srd/prestigeClasses/assassin.htm#)with a ranged weapon maybe? When you get into 30ft range you get sneak attacks. And when you are up close, you can make a death attack with a melee weapon. Does that fit your taste?

[Darg]

Iaijutsu fits the bill. You don't even have to be close. You just need to catch the opponent flat footed while using melee thrown weapons. Being an Iaijutsu Master makes it even better as you can add your cha bonus per die of damage you deal among other benefits. The only real adaptation required is the one strike, two cuts ability and all you have to do with that is make the action an attack action (3.0 action rules are different and the context of the description of the ability firmly plants it as an attack action, not a special standard action. Meaning you can use it with spring attack.)

[Voldine]

Looking for an attack that deals more damage when I'm really close, kinda like a shotgun. The idea is based mostly on Andrew Jackson's dueling, where he would tank a shot, walk up, and end the duel. I want to do something very similar: force enemy into a 1v1 (got that part already with a spell I found), then deal an absurd amount of upfront damage when I walk up. Preferably this would be a ranged weapon of some kind, but spells are cool too.

Have you, perhaps, heard of the infamous Locate City Bomb?