Kaal means Samaya or Time.

There are many examples of Power of Kaal in our scriptures ---

Vishnu Puraan, 5/15
After Krishn had gone to His Lok, when Arjun was bringing Dwaarakaa women, some Aheer attacked them and took away some women from him and he could not do anything. Frustrated as he was, he went to Vyaas Jee and told him his saga, then Vyaas Jee said to him - "Vyaas Jee said - "Don't feel like a shameless person. It is not proper for you to grieve like this. You should know that Kaal Gati is like this. Rise and fall of everybody depend upon Kaal. All things are created by Kaal, and are destroyed by Kaal, therefore know all this effect of Kaal and be patient. Hey Dhananjaya, Whatever glory you have described of Krishn, He is indeed like that. He is Kaal. He took Avataar only to kill those people. His work is over, so He has gone. When you alone killed Bheeshm, Drone, Karn etc, was it not the effect of Kaal on their life? When your time was good then Kaal favored you, now your time is bad so Kaal is favoring your enemies. Who is going to believe that you alone killed so many brave mighty people like Bheeshm etc; in the same way who is going to believe that you got defeated even by Aheer. Hey Paarth, This is all Bhagavaan's Leelaa."