First Unique Even Element

Input: nums = [3,4,2,5,4,6]
Output: 2

class Solution:
    def firstUniqueEven(self, nums: list[int]) -> int:
        freq = collections.defaultdict(int)
        removes = set()
        evens = []

        for i, num in enumerate(nums):
            if num % 2 == 0:
                freq[num] += 1
                evens += num,

            if freq[num] > 1:
                removes.add(num)

        for remove in removes:
            del freq[remove]

        for even in evens:
            if even in freq:
                return even

        return -1