head to head
Neither is simply harder - they are hard in different places. Little King's Story demands more variance; Portal 2 demands more optimization.

Optimization · Pure Optimization
A charming Wii strategy game about a boy king commanding citizens to build his kingdom.

Optimization · Pure Optimization
A first-person puzzle game where seeing the solution is the whole skill.
Little King's Story leans Optimization (Pure Optimization); Portal 2 leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Little King's Story
Real-time citizen flinging needs modest control
Portal 2
Portal placement requires some precision but timing is lenient.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Little King's Story
Scripted boss kings
Portal 2
No opponent; puzzles are static.
Little King's Story leans clearly harder on variance.
Little King's Story
Some treasure and event randomness
Portal 2
Puzzles are deterministic with no randomness.
Portal 2 leans clearly harder on optimization.
Little King's Story
Kingdom economy, job assignment and expansion planning
Portal 2
Solving the puzzle's logic IS the entire game.
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.