Just for fun, I created a theme party that only combats with their bare fists. And I'm not allowing any monk characters in. They're your typical mix of characters, not just fighters. So basically, every party member takes Improved Unarmed Strike as their first feat. Fighters, wizards, clerics. Everybody! It's not exactly an economical way to spend feats, or especially safe way to play, (my fighters can use martial weapons, I just won't let them). But I'm just messing around. They're actually semi-decent! I've been through a few battles already. I enjoy watching the literal hand-to-hand fighting animations.

I guess there will come a point where I'll need either slashing weapons, or +1 or better weapons. Then it gets tricky. I know there's a spell that turns your weapon into a +1 magic weapon temporarily. Could your fists count?

I don't think the spell is going to work on fists. Never messed with unarmed myself.
Druids have some spells to make animal companions natural attacks magical, but I don't think that'll work with fists either.

With craft magic arms and armor, or craft wondrous items, I think you'd be able to make some combat gauntlets. But then masterwork items requires you to clear emridy meadows first, and I can't see that being done barefist style.

You're doomed. Doomed.

Depends on what's allowed spell-wise. If he's liberal with how his spellcasters can cast then he should be able to pull it off no problem. If he's restricting himself to buff spells, it'll be tight.

I think one of the merchants in Nulb sells some masterwork items, without requiring you to quest for them. I forget.
But... One strategy I tried that works is casting tasha's hideous laughter on the giant, followed by web. He's prone, and he can't do anything, except get hit by you! Talk about kicking a man while he's down!

And yeah I'll be casting every spell available (except maybe ones that put weapons in your hands). So I imagine the spellcasters will be the workhorses.

We'll see if I'm doomed! I'm still making progress so far!

Hitting a Giant with a will save is always the best approach. Later on when you need to do this to a larger number of targets, the confusion spell works wonders.

If you're allowing any spellcasting, I don't see any real troubles with completion. There might be a few problematic encounters, but for most of the game the spellcasters can really carry the wieght.

Making good use of spellcasters you may be able to make it pretty far in the game, although I expect some of the enemies near the end of the game, which combine immunity to normal weapons with high spell resistance and high HP may end up being insurmountable to your party, due to your brawlers being unable to harm them, and your spellcasters not having enough firepower to take them down before running out of spells.

Can you put an enhancement bonus on gauntlets to allow an unarmed strike to hit powerful creatures? If so, I think he's fine to the very end.