Though Oogway from Kung Fu Panda doesn't get to show off his Badass Grandpa skills much, one flashback shows a fight with fellow badassTai Lung that lasts all of a couple of seconds. Oogway completely immobilizes Tai Lung with a few nerve taps. Shifu himself is no slouch, trouncing all of the Furious Five at once and holding his own against Tai Lung even though crippled by his regretful feelings.
The 2009 animated Pixar film Up has Carl Fredricksen, who's one heck of a badass old guy. Although he technically isn't a grandpa, since he couldn't even have kids. There's also Charles Muntz who was a famous adventurer when Carl was a child, and is still in better shape than him when they meet.
The 2006 animated Blue Yonder film Hoodwinked does this with Granny Puckett, who is a Badass Grandma for Red Puckett. After all, we're talking about a granny who does alpine skiing, skydiving, half-pipe skateboarding, surfboarding, and more, and much like Red, is proficient somewhat in karate.
Rafiki the Mandrill in The Lion King, who can take on a pack of hyenas as well as any lion.
Claude Frollo of Disney's The Hunchback of Notre Dame. Although he mostly makes his soldiers do all the work, he's quite capable of going after anyone himself. He's almost as physically strong as Quasimodo.