The Last Prime vs Biollante: who would win?

The Last Prime favored — Slight edge (~55%)

The Last Prime · Transformers · Power of the Primes

Tier

HIGH 4-C, up to 4-B

Attack Potency

Large Star Level, up to Solar System Level

Speed

Subsonic, up to Supersonic+

Durability

Large Star Level, up to Solar System Level

Biollante · Godzilla · Rose Form

Tier

HIGH 4-C

Attack Potency

Large Star Level

Speed

Immobile, up to Subsonic

Durability

Large Star Level

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