head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Execution · Pure Mechanics
Memorising brutal scripted patterns and executing them without a single slip.

Execution · Pure Mechanics
A movement-shooter demanding near-perfect execution chains to maximise style rank against scripted but relentless enemies.
Contra: Hard Corps leans Execution (Pure Mechanics); ULTRAKILL leans Execution (Pure Mechanics).
ULTRAKILL leans a little harder on execution, though the gap is small.
Contra: Hard Corps
One-hit deaths under relentless bullet pressure demand perfect inputs
ULTRAKILL
Style-ranked combat demands flawless movement, parries, and weapon-swap chains
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Contra: Hard Corps
Bosses are fully scripted setpieces
ULTRAKILL
All enemies are scripted; no adaptive human opponent exists
ULTRAKILL leans a little harder on variance, though the gap is small.
Contra: Hard Corps
Everything fixed once routes and patterns are known
ULTRAKILL
Enemy placement is fixed and fully readable after one pass
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Contra: Hard Corps
Memorising boss patterns, weapons and branching routes is mandatory
ULTRAKILL
Weapon synergies and ranked-route planning form a deep solvable system
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.