Going with the Tyranid.
If I am part of a hive mind and have the most awesome pet ever, I don't need anyone else. The description kind of implies that my own mind will be kept intact, so as a singular voice among the trillions of individuals there's no reason I can't take defacto command of them. If they let me keep my body (or, rather: copies thereof that I psychically project my consciousness into) I can even act as a mouthpiece or emissary before we eat the next planet in line. Kill me? Impossible; that's just a shell. I have limitless copies.
So we're going to eat the entire fucking cosmos until it forms a universe-spanning biological computer binding together all life that was and is, and live on in immortal perfection until the end of time. Neat!