When the LORD your God brings you into the land where you are entering to possess it, and clears away many nations before you, the Hittites and the Girgashites and the Amorites and the Canaanites and the Perizzites and the Hivites and the Jebusites, seven nations greater and stronger than you, and when the LORD your God delivers them before you and you defeat them, then you shall utterly destroy them. You shall make no covenant with them and show no favor to them.
What we see here is that God decreed that it was time for these people to die, and His method of choice to accomplish this was to have them killed by the Israelites.
The Bible tells us that God is ultimately the one who takes life (1 Samuel 2:6; Job 1:21), which is fitting as He is the one who provides it in the first place (John 1:3; Hebrews 1:2).
With respect to the Canaanites, God demonstrated His just nature in His judgment upon them. According to scripture, the Canaanites had been sacrificing their children to gods that didn't exist (Deuteronomy 12:31), practicing homosexuality and bestiality (Leviticus 20:23), sorcery and witchcraft (Deuteronomy 18:14), all things that they ought not to have done, and knew that they ought not to have done (Romans 2:15).
In blatantly disobeying the consciences God gave them, the Canaanites were requesting that their Creator destroy them.
Our God is a just God, but He has also offered us forgiveness for our offenses through His Son, Jesus (John 3:16).
If you have not asked God to forgive you for your crimes against Him through the payment provided by Jesus (Isaiah 53:5), you stand in the same position the Canaanites were in. Expect judgment.