I will answer Japan and India.
Subtle flavor
Tsukiji Fish market in Tokyo has sushi like no other. Fresh catches every morning. You have to get there early to wait in line for the catch of the day and it can be pricey but well worth the wait, I have never tasted Tuna so perfectly balanced with fat and muscle that it melts in your mouth as a slice of butter would.

Intense Flavor
Southern india's west coast is known for their spicy fish curries and grilled dishes that are mouth wateringly good.