Strategy: Amadeus is a pure damage hero with no support utility whatsoever — no army-wide buff, no control, no healing. Every point of value he provides comes from his own numbers, which means the entire case for running him rests on those numbers being big enough to outweigh what a support-oriented Infantry lead like Alcar or Eric would otherwise bring to the march. Combo Slash's three-hit AoE at 224% Attack per hit clears that bar comfortably when fully invested — one of the highest raw burst numbers among Infantry skills in the early-to-mid roster.
Onslaught adds a low-Health power spike similar in spirit to Long Fei's — both heroes get stronger below 50% Health — but Amadeus only gets the offensive half of that design. Long Fei pairs his below-50% Attack bonus with a matching 60% damage reduction; Amadeus gets +48% Attack and nothing defensive to go with it. That makes him considerably more fragile in the same situation — dangerous, but genuinely risky to leave in an extended fight rather than pulling him out once he's wounded.
Double Parry, his exclusive skill, is his only real defensive tool: a flat -30% damage taken. It helps, but it doesn't change the fundamental profile — he's a glass cannon by design, not a misunderstood tank.
Skill priority: Combo Slash first for the core burst, Onslaught second to maximize the low-Health spike, Arcane Swordship third — its passive per-slash damage is modest individually but adds up over a longer engagement.
He rewards full investment more than most Gen 1 heroes — a partially-starred Amadeus is mediocre, since his entire value proposition depends on his damage numbers clearing the bar a support hero's utility would otherwise fill. If you're spending to fully star him up before Gen 5-6 alternatives, he's a strong pick; if you can only half-invest, a support-oriented Infantry lead serves you better.