Mounted Dreadknight

The counter is a race condition given a body. A 5/4 trampler for five is already fine attacking into metal, but the conditional +1/+1 rewards a deck that has already gotten under its opponent: chip in early, and this arrives as a 6/5 that shoves damage past a chump. The condition reads any opponent losing life this turn, not just combat damage from this creature, so you can sequence a direct-damage spell, an opposing painland activation, or an aristocrats drain ahead of it to make sure the counter comes along. And because that counter is granted by a replacement effect baked into how the creature enters (not a trigger you can respond to or fizzle) there is no window to strip it once the life loss has happened: the game state on your main phase is already settled before you tap the mana. Building the payoff as an enters-with condition rather than an attack trigger is what does the strategic work. It turns your earlier aggression into a permanent stat bump, so the card scales with how the game has been going rather than what it does in isolation. Drop it onto a stalled board and it is a vanilla trampler; play it as the follow-through on a plan that has already drawn blood and it comes down oversized and awkward to block profitably. Vampire Knight is the right tribal furniture for aggressive red with a black splash, but the counter itself is color-agnostic incentive: it asks you to be ahead, and pays you for staying there.