Basically anyone who isn't human.
The Death Note only works on humans so anyone not human, Goku, Yusuke, Ichigo(although he is half human, half shinigami, half quincy, half hallow, not sure how it works on halfs), etc. they can easily beat Light.
Not to mention Light has to know their name.
Does this mean Light has prep and the other character has to beat him before he can write down a full name?
Does the other character know Light is trying to kill them and their objective is to stop him before he writes down the name?
Misa would make it much easier since she can see their name. Light would have to figure out their real name before he could write it down. Basically without prep hes useless.
Unless he up against a character that says their name a lot aka "My name is Luffy and I'm going to be King of the Pirates," he has really no chance if the other character knows Light is trying to kill them.
Misa kills more than Light since she can find out their name right away, but lose to all people not human, and are faster then either writing down their full name.