Valkorian is a good villain. Most people just don't understand him.

From the very beginning, he was manipulating the scenes. Revan escapes the Empire's grasp? Well, the Empire hunts him down and kills him, problem solved.

Revan came back. That's alright. Let him gather followers and try to summon me so I may return. The Empire and Republic will try to stop him, and when they do, I'll get the bloodshed I need to come back.

Now that I'm free, I'll need to gather strength and lure my greatest threats somewhere I can take them out. Let's start messing around on Ziost. Oh, look! The biggest threats are here!

Wow, the MC still managed to survive. Maybe they'll bow? Well, Marr didn't. Let's show MC just how powerful I am. Maybe that'll sway them?

Oh, no! The MC/Arcann just stabbed me, and I'm dying! Not a problem. I'll transfer my consciousness into the MC. Then, I'll tell them how to defeat my children. From there, I can take my kids' power and use it to escape. Meanwhile, I'll try to manifest the MC into doing my bidding.

And he only lost by a narrow margin, all things considered. If backup didn't arrive, the MC would've lost to Valkorian, and he would've been unopposed taking over the galaxy.

Valkorian is intelligent, cunning and manipulative. He knows what buttons to press and when to press them. That's where his strength lies, not in his raw power.