Acidic Slime

Green has never killed creatures cleanly, but it can answer almost everything else, and this Ooze is the platonic version of that bargain stapled to a body. The enters-the-battlefield trigger reaches across three of the most awkward permanent types to remove (an artifact, an enchantment, or a land), and unlike a Naturalize-style instant, it leaves a creature behind to keep working. That body is the part that earns the five mana. Deathtouch on a 2/2 turns the disruption into a recurring combat deterrent: anything that blocks or attacks into it dies, so the same card that strips a problematic permanent also taxes the opponent's offense for the rest of the game. The trigger is unconditional and the target list is wide enough that the card almost never sits dead, which is the quiet reason it has outlasted flashier value creatures: it does removal work in a color that otherwise cannot, then converts the leftover stats into pressure. Note the absence of a "may" clause; the trigger must resolve if any legal target exists, so if one of your own permanents is the only thing it can hit, you destroy it. That bluntness is the design honesty here. It does one job, it does it on a stick, and the deathtouch ensures the stick is never just a 2/2 once the trigger has resolved.