Space Ishtar vs Eight: who would win?

Space Ishtar favored — Slight edge (~55%)

Space Ishtar · Nasuverse · Prime Ishtar

Tier

LOW 2-C, up to 1-C

Attack Potency

Universe Level+, up to Complex Multiverse Level

Speed

Omnipresent

Durability

Universe Level+, up to Complex Multiverse Level

Eight · Dragon Quest · End of Game/Postgame

Tier

LOW 2-C, up to 2-C

Attack Potency

Universe Level+, up to Low Multiverse Level

Speed

Immeasurable

Durability

Universe Level+, up to Low Multiverse Level

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