DFS || Python
Code

# Code
```python3 []
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def subtreeWithAllDeepest(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        def dfs(node, depth):
            if not node:
                return (None, depth + 1)

            leftNode, leftDepth = dfs(node.left, depth + 1)
            rightNode, rightDepth = dfs(node.right, depth + 1)

            if leftDepth > rightDepth:
                return (leftNode, leftDepth)
            elif rightDepth > leftDepth:
                return (rightNode, rightDepth)
            return (node, leftDepth)

        node, _ = dfs(root, 0)
        return node
```
['Python3']