What are some examples of when Maniac Magee is compassionate?

Maniac shows compassion when he saves Arnold from Finsterwald's, teaches Grayson to read, and shares his pizza with the little runaways.

Maniac may be weird, but he has a good heart. One example of when he baffled the town’s youth and showed kindness at the same time was when he rescued a boy who some big kids were harassing.

Finsterwald was one of those neighborhood boogeymen. No kid would go into his yard to retrieve a ball or hang out in front of his house. The older kids were teasing Arnold by sticking him in Finsterwald’s backyard. Maniac helped him dispassionately and without question.

The phantom Samaritan stuck the book between his teeth, crouched down, hoisted Arnold Jones's limp carcass over his shoulder, and hauled him out of there like a sack of flour. Unfortunately, he chose to put Arnold down at the one spot in town as bad as Finsterwald's backyard—namely, Finsterwald's front steps. (Ch. 5)

This is part of how Maniac developed his legend status, with crazy stunts like this. All he knew was that the kid was in distress, and it never occurred to him to not help. He then sat on Finsterwald’s porch and read his book.

Another example of Maniac’s compassionate personality is when he teaches Grayson to read. Grayson is an old man who takes Maniac in when he finds him sleeping in the buffalo pen. Maniac never questions Grayson’s somewhat odd lifestyle. When he realizes that Grayson can’t read, he teaches him.

Then they went to the library book-sale racks and bought about twenty old picture books, such as The Story of Babar and Mike Mulligani Steam Shovel and The Little Engine That Could. 

Then they went to Woolworth's for a small portable blackboard and a piece of chalk. (Ch. 27)

Through Jeffrey’s patience, Grayson learns to read rather quickly. When Grayson dies, he is devastated. He has to go on the run once again and go back to being Maniac Magee.

Finally, there are the two kids with the pizza. Maniac finds two kids, Russel and Piper, who have run away. He gives them his pizza and makes sure that they get home. Maniac later finds out why they ran away from home. He does his best to create order in the chaos.