Who is Todd from A Dog's Purpose and what is their importance?

Todd is a boy the same age as Ethan. He moves into the neighborhood with his older brother, Drake, and is younger sister, Linda. At first Ethan played with Todd but he soon realizes that they were very different. Todd likes to set off firecrackers and has a mean streak. This mean streak has a dark side. Todd doesn't want anyone else to be happy or have anything. He also doesn't like animals. He lures Bailey into his room and tries to get him to sniff airplane glue, but Bailey escapes with Linda opens the door. Todd particularly dislikes Ethan. He is extremely envious and Bailey can smell the hatred he feels for Ethan. Todd tries to kill Bailey with poisoned meat and Bailey smells Marshmallow on his pants when Marshmallow is missing. She never does return. The worst thing he does, though, is setting fire to Ethan's house and causing Ethan to be so badly burned that he loses his football scholarship and becomes a cripple. He also loses Hannah because of this.