48 you can't do it thats the problem. you need to silence 2 minions and kill 3 if you want it to have no effect on the game.
killing Dr boom is already easy but it still leaves you with 2 1 attack and 1 defense minions that deal 1 to 4 damage to a random enemy once they die
thus as a recap you get a total value of an 9/9 plus 2 to 8 damages to 2 random enemy's once it dies.
And because the damage on death are other creatures you can't just silence it and big game hunter if afterwards.
damage is not restored at the end of a turn so even if the boombots didn't kill a creature it still made it easier to kill it later in the game.
Because the damage is random it can hit creatures that you normally can't target thus it being random is also almost an upside.
I am sorry but where is the downside of playing this guy? You get 1 mana every turn so unless you make an deck that can deal at least 30 damage in 6 turns you can't win before it hits the board and that doesn't even factor in that it can hit the board earlier for certain decks.