A lab accident gives a hound named Shoeshine some serious superpowers -- a secret that the dog eventually shares with the young boy who becomes his owner and friend.
No, though there is a fakeout death at about an hour, eleven minutes and forty seconds in where the titular Underdog appears to have died, his owner picking up his unconscious body and sobbing. He does quickly reveal himself to be alive, but it can be a distressing image.
The story follows a single father and his son, with the son mostly looking after Underdog.
Mention of something having happened recently at the beginning of the movie and the son reassures his dad "I'm okay, really" but nothing specific is said
At 35:51 in:
Son is talking to Underdog and mentions "when Mom died" in passing but worth mentioning as it could catch someone off guard.