Answer:
The sentence which contains a comma error is the following one:
The little, old man could hardly stand up due to his painful arthritis.
Explanation:
Two adjectives in a row are used to describe the man (little and old), and because of that there should be no comma separating those two words. The proper way to rewrite the sentence would be the following one:
The little old man could hardly stand up due to his painful arthritis.
