Settra pretty rarely actually uses his lasers and magic unless he's at a major range or needs to counterspell, he literally went melee with Arkhan across an entire battlefield during the End Times. That's also why his ass got knocked from first key to second key, he entered melee and just refused to dodge an enchanted weapon. But Angron is also not particularly known for dodging so that evens out.
Something you might be surprised also evens out is skill. They're both scaling to the same guy, Skarbrand. So their skill is comparable at minimum. So it comes down to this: Is Angron's range and AP/Dura advantage good enough to outdo Settra's LS, movement speed, and chariot?
Well... Angron's range means zilch, Settra has like 4 instances of fighting Dragon Ogre Shaggoths, including Kholek Suneater. Who is like, bigger than the biggest Titans, he can literally look over the walls of Praag with ease... and Angron isn't really used to fighting at an LS disadvantage, which means Settra's Chariot is gonna be a pain in the ass for him.
Should note this though: Aethyr Manipulation and Psyker powers, while they have the same source, are inherently different things. It's why we didn't merge those pages. So technically Settra could hax Angron... though vice versa is not true. Settra has god-rated resistances. Angron ain't haxing him ever.
If they were both on foot I'd say Angron would take this high diff. But they're not. Settra is on a chariot, and that chariot is exerting Class M forces and is moving at supersonic speds, which basically means that unless Angron acts grossly out of character, he's just gonna get run over repeatedly and by the time he either breaks it or Settra decides to fight him hand to hand, Settra wins the melee battle off the fact of Angron already being badly injured.
So Settra high diff. Use Gotrek next time, it'd be funny.