Interestingly enough, valko doesn't seem to be smiling in much of his promo art, unlike most of the other lis. Zayne doesn't smile much either, but he's got more of a stoic neutral expression while valko straight up frowns.
I think, based on the few images and teaser we got, valko's more of a serious and tough person, at least on the outside.
I'm going to use sylus as a comparison because everyone's already comparing them so it'd be easier I guess, but sylus smirks in his promo material most of the time. We know that sylus is sly and charismatic, so it makes sense. We do have one image where valko's smiling and it's in the mobile version of the lads website.
Oh yeah, this picture also shows more information about him. His tagline is "A wild, unbound will, surrendered only to you." so I'm assuming that he does at least intimidate people in some kind of way. But I think "surrendering" could mean that he's sweet to the mc, at least once he gets to know her.
ALSO CONTRARY TO THE ENTIRE INTERNET, VALKO IS NOT A CEO. HE IS A CHAIRMAN. IF THE CEO IS THE LEADER OF THE COMPANY, VALKO IS THE ONE OVERSEEING THE LEADER. PLEASE SKIM THROUGH THIS ARTICLE EXPLAINING THE DIFFERENCE BETWEEN A CEO AND A CHAIRMAN BECAUSE I WILL NOT ACCEPT FACTUALLY INCORRECT SLANDER.
Sylus, in fact, more closer to an actual CEO than valko, despite valko having an actual corporate title. Because Sylus is the LEADER of an organization and valko is not. If sylus and valko were under the same military, Sylus would be commanding troups while valko would be the general and coming up with strategies.
So, based on his job description, I'm assuming that valko's more introverted than sylus, or maybe he's just not as charismatic. I could see him being quiet and mysterious based on what we've seen, but not in the icy and cold kind of way like zayne is. His evol type is "metalization", so I'm thinking he's strong and more confident in himself. All the lads men are clever in some kind of way, and I think valko's cleverness could be in a sneaky, less flashy way. Like he doesn't outright show that he's been orchestrating things but nudges here and there to have his way.
I'm really hoping he's just scary on the outside but sweet on the inside. Also, he looks really cute with a smile and I hope we get to see him like that more :)