Super 17

Super 17 is the ultimate android, formed when Hell Fighter 17 — a replica constructed in Hell by Dr. Gero and Dr. Myuu — phases through the barrier between Hell and the living world and merges with the real Android 17. The resulting fusion has near-perfect ki absorption, making most energy attacks useless against him. Super 17 was eventually defeated when Android 18 triggered the real 17's suppressed emotions, breaking the Hell Fighter's programming long enough for Goku to attack from the inside with a Dragon Fist.