King of the hill - When there is a group, there is usually someone who is the most powerful in the group. To refer to that person, the most powerful in the group or like the head of the group, we say he/she is the king of the hill.
1. Tendulkar is king of the hill of Team India.
2. When it comes to wrestling, Undertaker is the king of the hill.
3. I don't understand why he did that, maybe due to his being the king of the hill.