Stiyl Magnus vs Shen (Undead Unluck): who would win?

Shen (Undead Unluck) favored — Slight edge (~55%)

Stiyl Magnus · Toaru Majutsu no Index · Base

Tier

7-A, up to 5-B

Attack Potency

Mountain Level, up to Planet Level

Speed

Sub-Relativistic

Durability

Small Building Level, up to Country Level

Shen (Undead Unluck) · Undead Unluck · Base

Tier

7-A, up to HIGH 7-A

Attack Potency

Mountain Level, up to Large Mountain Level

Speed

Hypersonic+, up to Massively Hypersonic

Durability

Mountain Level, up to Large Mountain Level

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