head to head
Neither is simply harder - they are hard in different places. Red Faction II demands more execution; The Witcher 3: Wild Hunt demands more optimization.

Execution · Practiced Mastery
A destructible-environment FPS relying mainly on shooting execution.

Optimization · Practiced Mastery
A narrative action RPG where build planning matters more than reflex execution.
Red Faction II leans Execution (Practiced Mastery); The Witcher 3: Wild Hunt leans Optimization (Practiced Mastery).
Red Faction II leans clearly harder on execution.
Red Faction II
FPS aim and movement against enemies
The Witcher 3: Wild Hunt
Combat timing matters but generous dodges forgive sloppy play.
The Witcher 3: Wild Hunt leans a little harder on reads, though the gap is small.
Red Faction II
enemy soldiers use scripted AI behavior
The Witcher 3: Wild Hunt
Enemies use fixed AI behaviours; no adaptation.
The Witcher 3: Wild Hunt leans a little harder on variance, though the gap is small.
Red Faction II
minor spawn and damage randomness
The Witcher 3: Wild Hunt
Loot rolls and minor combat variance only.
The Witcher 3: Wild Hunt leans clearly harder on optimization.
Red Faction II
weapon choice and level routing
The Witcher 3: Wild Hunt
Builds, alchemy, and quest routing reward planning.
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.