It sounds like your 2 year old doesn't understand that what they are doing is wrong. Or simply doesn't care that what they are doing is wrong. Most 2 year olds aren't interested in reasoning with you, at least ours never were. However, they can understand action and consequence as early as 6 months old. As they haven't really developed their own moral compass at the age of 2, that responsibility falls to you to be their moral compass.
Your two year old needs to understand that when he does something he isn't supposed to do, there are consequences that he doesn't like or enjoy. And he needs to understand that if he does something well, there are consequences that he does like and enjoy. In our house we call this principle Discipline and Encouragement. Though I'm sure a phycologist has more esteemed terminology.
When it comes to Discipline and Encouragement, you need to make sure that you and your spouse/partner are clear and together on what that looks like for each one of your kids and the stages that they are in. Have that conversation often as they move into new stages and seasons of life. And when it comes to the Discipline piece, make sure that your anger or frustration never get in the way. Sometimes that might even mean that you defer to your spouse/partner until you are able to calm down. (My wife and I often experience this).
It's okay if they cry. You can cry with them if you need to. The goal of parenting isn't to keep your kids from feeling pain (though we all try to avoid it when possible.) The goal of parenting is to help them become respectful and productive members of society as they begin to come of age. You obviously wouldn't want a 17 year old kicking his friends in the face every time he gets in the car with them. I have known some 17 year olds who do just that and it isn't very pleasant for anyone in the car, just as it isn't pleasant for you at this stage.
Momentary heartache that produces a lifetime of fruitfulness is infinitely better than momentary heartache that produces a lifetime of heartache.