Just curious to see everyone elses opinoins
traditional gryphons are part eagle and part lion, so they would have strenghts and weaknesses from both. they are very big, but are still able to fly very well. they would probably have to be very lightwieght, with birdlike bones and a fast metabolisim. Being predators, they would also have to be very tough physically to withstand prey attacks when hunting and fighting with themselves and other creatures.
Harpy eagles, some of the larges eagles in the worlds, can wiegh up to 20 pounds, and can carry prey up to half it's own wieght. it's hallux talons (or rear talons) are sometimes larger than a grizzly bear's claws. Trained redtails (in falconry) have been known to take prey as large or larger than themselves under the right conditions, although they would very rarley do it it nature, if ever. Large female redtails can wiegh up to 4-5 pounds.
harpy eagle on the fist
redtail hawk and rabbit