The idea is to recursively traverse tree in a pre-order fashion. Root is considered to be at zeroth level. While traversing, keep track of the level of the element and if its current level is not equal to the number of elements present in the list, update the maximum element at that level in the list.
Largest value in each level of Binary Tree: https://www.geeksforgeeks.org/largest-value-level-binary-tree/