Scarab King in normal mode, if you have either of these self-shield champs
https://ayumilove.net/raid-shadow-legends-shield-skill-champions/
Try bring him/her to Scarab King and let him/her fight alone, he/she will kill Scarab King. In case it fails, upgrade the champ & repeat again & again.
I use MM, Gala Longbraids & Madam Serris, in the end Madam Serris kills him.
P/S:
1) I am building Vergis for him.
2) Scarab King is an OP, with buggy counter-attack, instead of CA only un-shielded champs, he CA all, that means the less champs you fight him the better chance to limit his buggy CA.