I am not 100% sure those are bot accounts. They have favored a variety of cards, some of them made by reputable Cardsmiths. Plus, I have seen some of those accounts in the far past, probably before Magic-123456789's account was created. But just a warning to Magic-123456789 and others: MTGCardsmith takes bot accounts very seriously. If you are using them, which you probably aren't, we would highly advise you to stop immediately,
That being said, how about some nice constructive criticism?
1): When you write an ability, always add a : sign after the mana costs and tapping/untapping symbols. This makes your cards look much more professional.
2): If an ability has an additional cost, like paying energy on this card, put a comma instead of a : sign after the mana costs and put a : sign after the additional costs.
3): Periods are important for cards. Don't forget them!
4): Instead of "X: You get X plus two (nrg),' I would add an additional clause to the destroying ability like '1B: Destroy target creature. You get X (nrg), where X is the destroyed creature's toughness.
5): I would highly suggest using 'Human Assassin' instead of the card's title in the creature type box.
So I would format the card like this:
1B: Destroy target creature. You get X (nrg), where X is the destroyed creature's toughness.
Most likely will come back to this card, as I am unsure on the balance of the card. It's just the last iteration of the five that I went through. I know it's irregular for an uncommon to revolve so much around exile, but it's something I would like to try.
Edit: It should say other target creatures you control (on the second ability).