To explain my own choices a little more, on the off-chance that anyone cares...
I like Duelist as a background because the combination of combat and social experiences are quite appealing, and gives the protagonist a little agency. If they have some ability to fight and to communicate with others that's good, because it has more of a practical effect on being able to influence the world around them. Leaning hard into mental expertise seems like it's likely to result in a powergame'd psyker character, which is an idea that I loathe. I wouldn't hate Veritor as a choice though.
I'm not a big fan of Divination as the protag's primary powerset as I don't think that the ability to see the future very frequently translates to interesting stories. It's too introspective, too detached from the action and present of what's going on. It
can be done well, sure, and I have no doubt that
@Maugan Ra can write an interesting story in spite of it, but it's not the kind of thing that I think generally makes for an interesting read.
Telepathy is in a similar boat; being able to read the minds of just about everyone the character comes into contact with, and dominate others to bend them to their will, is just narrative poison to me. I understand that the protagonist would have limits to their power that present it from being such an easy 'I Win' button, but it's another one of those powers that, when used correctly, should often resolve what might have been an interesting conundrum too easily. Telepathy is only really interesting to me when it's extremely weak; we've been told that this is a choice of the protagonist's core (strongest) powerset, so if telepathy is their core power, and is still weak enough to be interesting, than their other powers would be even weaker.
Telekinesis isn't a choice that I hate. I could go for it but there's not much really drawing me to it.
I like Biomancy the most though. It's a power that has a lot of narrative uses while not seeming like it's too overpowered. It has combat and utility appeal, but in the world of 40k that won't make you invincible if you get on the bad side of something/someone powerful. I think it also goes well with the Duelist background.
Vincenzo Leonardo Borgia, because, Malfi. It's the planet of the vendetta, and doesn't that mean we need an appropriate Italian-esque name?