Reading the comments, I see that this was originally an all-killing card and you changed it to to targeting. I see this as a good thing; It would've been too powerful, especially if you consider the possibility of abusing it in mono.
So far, we have only one non HP-related kill*: The Freeze+ Shockwave combo. This uses 2 cards of two different elements, and 3 quanta overall, so using it is actually card disadvantage (while cards like Squid and perma shield can be used too, it's not so fast and secure of a kill than freeze+wave).
Now, let us compare this card and the possible synergies of it (in-color synergies, even) to the above. The first thing that comes to mind is virus+this. On-color, two cards used, and two turns needed since it takes one turn while the opposing creature suffers the damage.
Even if you use other, non-card disadvantage tools as a means of damage (Fire Shield comes to mind), the creature will always have a round to attack or use its abilities.
If you want to instantly kill a creature, then you have to use a direct-damage spell in conjunction with this card, just like with Freeze+Shocwave.
Conclusion: This card is a full turn solwer than an already existing combo to kill creatures regardless of their HPs. This card also relies on another card to kill a creature, but unlike in the other case (the freeze+ shockwave combo), this card is completely useless if the other half of the combo is not in the player's hand.
While the abuse potential with on-color cards like Plague is high, note that it never causes actual card advantage. I think that this is the biggest problem of this card, so what I'd do is add a cantrip so the card's text becomes "Kill the target wounded creature. Draw a card."
Another option might be (an even better one, although I don't know if it can be coded into the game) is to remove the situational nature of the card with something like this:
3
"Choose one: Kill the target wounded creature. OR draw a card"
*
Yes there are things like Oty and Maxwell which are not traditional HP-related, but still they are fairly situational.