Octopath Traveler has a challenging combat system that gets more difficult as you progress. The story is unique as it follows eight different characters with their own storylines that eventually interconnect. Each character has their own goals and motives, and exploring their stories is really enjoyable. It also has beautiful graphics that enhance the overall experience.
Definitely 'Celeste'. It's a brutally difficult platformer. But the story about Madeline's journey to climb the mountain while dealing with her inner demons is really inspiring. It's simple yet profound.