Annihilarrgh vs Kamen Rider Black RX: who would win?

Kamen Rider Black RX favored — Favored (~65%)

Annihilarrgh · Ben 10 · Base

Tier

1-C, up to 1-B

Attack Potency

Complex Multiverse Level, up to Hyperverse Level

Speed

Immobile, up to Immeasurable

Durability

Below Average Human Level

Kamen Rider Black RX · Kamen Rider · End of Series (41-47)

Tier

1-C

Attack Potency

Complex Multiverse Level

Speed

Transonic, up to Immeasurable

Durability

Complex Multiverse Level

A heuristic estimate from normalized VS Battles Wiki stats: tier, attack potency, speed and durability.