Mima

The reason the Roaring Knight is so strong is because they have fused with Kris' original soul. It's a hybrid.

To prevent Kris' death, he's given the Red Soul as a temporary replacement. But this doesn't help the fact that this fusion is inherently bad for both.

Episode 3 reveals a flashback of what are likely, Echidna, Reid, Farsale, Hoshin, Satella and Flugel.

The current party has 8 people, 6 if you discount Meili and Rem, who both did not exactly choose this.

You have Beatrice, Julius, Ram, Anastasia, Emilia and Subaru.

Beatrice is Echidna's daughter. Reid and Julius are both swordsmen, Hoshin and Anastasia are both famous merchants from Kararagi - Anastasia literally took his last name. Satella and Emilia are carbon copies, both have unreal amounts of mana, both are capable mages and they share a relationship with subaru. Subaru and Flugel share too many similarities to count.

The only person who don't share a connection are Farsale and Ram, but if we apply Ram's motivation to his, it's likely Farsale is here on behalf of his Kingdom. They probably both arrived here to protect something they both love.

One embarked on a journey to save the world. The other went to save the victims in priestella and Anastasia.

Her only reason to exist is for bear, and yet, he's shallow and empty. He's a walking body with no substance. He'll never love her, he'll be anything other than a sad, pathetic and selfish man, who lives in an entirely different plane of thought.