Kaiju No. 9 vs X Parasite: who would win?

X Parasite favored — Slight edge (~55%)

Kaiju No. 9 · Kaiju No. 8 · Post No. 2 Absorption

Tier
6-B, up to 6-A
Attack Potency
Large Country Level, up to Continent Level
Speed
Massively Hypersonic, up to Ftl
Durability
Large Country Level

X Parasite · Metroid · Base

Tier
6-B
Attack Potency
Country Level+
Speed
Sub-Relativistic
Durability
Unknown

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