Okay. Dumbass build time incoming.
Since the new campaign I'm eventually going to get roped into starts at level 8, I've had to create a character for that level and as such have discovered that level 8 is a particularly curious beast of a level in the variety of builds it can support.
And so it is that I mashed together another such dumbass build this evening.
Scourge Aasimar Storm Barbarian 3/Warlock 5 (There are a couple picks for this, which I'll get into later). We take the Desert path for barb, and pick up Cloak of Flies as a level 5 invocation.
Cloak of Flies can technically be up indefinitely (provided we don't get knocked out), so it doesn't eat into action economy so long as you're okay with buzzing more than your local swarm ranger all the time. Entering into a fight, we can use our racial action and the rage bonus action on the first turn, at which point we're in full Radioactive Randy mode.
Everyone within 10' of you will take 2 fire, 4 radiant damage every turn (you also take the 4 radiant, but as an Aasimar you're resistant to radiant damage sooo...), and everyone within 5' will take an additional CHAmod poison. No saves for any of this, it just happens throughout the course of a round (start of enemy turn for CoF, end of your turn for Scourge, and bonus action on your turn for barb burn).
Now, you basically can't stand anywhere close to the rest of the party thanks to your awful technicolor radiation. Also a very significant portion of your damage comes from a once-per-long-rest ability. Additionally, there are some curious hangups with this build if we want to try being relevant outside of our nuke aura, which I'll go into here with talking about patron options:
Fiendlock seems like the obvious choice, thanks to the bonus tempHP whenever reducing something else to 0. This is especially entertaining seeing as CoF gets calculated at the start of an enemy's turn, and can potentially top us off multiple times in a round outside of our turn. We also get a couple chances on our turn, once with the fire aura from our bonus action (before we take self-inflicted damage), and once from the radiant aura as our turn ends (most likely after we take self-inflicted damage), giving us several opportunities to mitigate the damage we're eating thanks to being in the thick of the frontline while also sunburning ourselves.
For Fiendlock, we'd obviously want to pump CHA as much as possible for both CoF and tempHP, and the additional synergy between those two. ...however, by doing so we leave ourselves without any particularly good ways of dealing normal attacks, except by potentially taking Pact of the Tome and going for shillelagh. But that'd require a rageless round of buffing for a fight, which we may or may not be keen on spending. Furthermore, it locks us out of the synergies found in...
Hexlock, which is also an obvious choice, but it's an obvious choice for everything so that doesn't make it special here. This lets us use CHA for weapon attacks too, and taking Pact of the Blade means we can open up two attacks per action via Thirsting Blade, as well as Eldritch Smite which allows us to still use our spell slots even when we're raging (since it's technically not a spell). The issue here, however, is that if we're following leveling rules we technically can't have Thirsting Blade, Eldritch Smite and Cloak of Flies all at once at Warlock 5, since they're all level 5 invocations. One of them has to go. And the Hexblade's curse also uses a bonus action, but this one can be used while raging so it's less of a biggie. Not a huge amount of synergy there, but it's at least usable. Have to forego your fire damage for a round though.
If you do go the Pact of the Blade route, a couple more levels in Barbarian will get you extra attack for free, letting you replace Thirsting Blade with something else.
Now, is being able to deal about 10 damage to everything within 5' particularly overpowered? ...well, no. I just wanted to make a character stacking as many damaging auras as I could, because I thought it was funny.