head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Unravel Two demands more optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
A co-op yarn puzzle-platformer where two tethered characters solve levels together.
Grand Theft Auto V leans Execution (Practiced Mastery); Unravel Two leans Optimization (Practiced Mastery).
Grand Theft Auto V leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Unravel Two
Light platforming plus two-character swing coordination
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Unravel Two
No adaptive opposition, co-op only
Grand Theft Auto V leans a little harder on variance, though the gap is small.
Grand Theft Auto V
Some mission and lobby randomness.
Unravel Two
Fixed levels, fully visible
Unravel Two leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Unravel Two
Puzzles solved by routing two yarn characters together
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.