Mal'damba is the best healer for duels, if the Androxus is foolish enough to get close to you where you can comfortably hit your shots and the reload stun you CAN win, but if he doesnt good luck waiting for respawn.
Unless your Champion's basic attack is hitscan, like Viktor or Tyra, you'll be hard-pressed to hit Androxus while he's airborne. Wait for him to land, if you can.
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Androxus is great at short distance but he also can do much from long distance. The best way to counter him is bait him to use Reversal unnecessarily and force him to waste all Nether Steps and just stay grouped up.