Unfortunately nothing is going to be as versatile as [[Brotherhood's End]] if you're looking to recreate it :( It's a really unique sideboard option in that it helps again creature matchups, the artifact decks, or even to get rid of sideboard artifacts.
Instead of finding the next best replacement, I would probably try to prioritize these spots to directly address one thing you're having problems with.
- For problematic artifacts and Bowmasters, I've found [[Cast into Fire]] to be really strong.
- If it's Phoenix decks or smaller aggro decks, [[Anger of the Gods]] is a good choice if you have them.
The rest of these aren't as good:
- [[Sweltering Suns]] was a previous maindeck sweeper I ran in Jeskai historic a while ago because I could cycle it in matchups it wasn't necessary. Might not be a good option as a SB card though.
- [[Storm's Wrath]] is a pretty good red sweeper but costs 1 more and might hit more of your own creatures.
- If 5cmc is ok and you need it to hit walkers (and 5 damage isn't a problem), [[Burn Down the House]] or [[Hour of Devastation]] would be an option.
- If 3cmc is a must [[Into the Fire]] does 2 damage but has another mode.
