使用kruskal算法创建更糟糕的案例场景

I have an implementation of Kruskal's algorithm in C++ (using disjoint data set structure). I'm trying to find possible methods of creating worse case scenario test cases for the total running time of the algorithm. I'm confused however on what can make the algorithm result in a worst case scenario when trying to create test cases and was wondering if anyone here might know of possible scenarios that would really make Kruskal's algorithm struggle.I have an implementation of Kruskal's algorithm