How does sir kay Arthur's step brother show that he doesn't have what it takes to be king?

Sir Kay, Arthur's stepbrother, demonstrates his unworthiness for kingship through his arrogance and lack of honor. When given the opportunity to pull the sWord from the stone, he attempts to claim the glory for himself rather than acknowledging Arthur's rightful claim. His actions reveal a self-serving nature, prioritizing personal ambition over the nobility and responsibility required of a true king. This stark contrast to Arthur's humility and virtue underscores why Kay is unfit to rule.