Firemaw Kavu

The leave-the-battlefield trigger is the whole point. Two damage on the way in is a footnote; four damage on the way out is the reason to bother, and echo is the lever that gets you there fast. The trick is that echo forces a choice. Pay the echo cost once and you keep a body for as long as you want it; refuse it and the creature sacrifices itself on your upkeep, dealing four damage to a target as it goes. That turns a downside keyword into a delivery mechanism: a six-mana creature that would otherwise fizzle into a sacrifice clause becomes, instead, a Flametongue Kavu's worth of removal stapled to a deferred second shot. The design lineage runs straight back to Flametongue Kavu, the enters-the-battlefield burn body that defined what a red value creature could be; this one splits the same payoff across two triggers, the first immediate and mandatory, the second held in reserve until the Kavu leaves. The 4/2 frame matters too: fragile enough that you rarely mind feeding it to a sacrifice outlet, large enough to trade up in a pinch. Anything that flickers, sacrifices, or reanimates it stacks both triggers into a six-damage swing across two targets, which is the strategic axis the card was built for. Echo reads as a tax on the front half; here it functions as a fuse, offering a cheap way to cash the creature in for the leave trigger, and rewarding any deck built to control when and how the creature exits play.