The difference between Regretful and Sorry

When used as adjectives, regretful means full of feelings of regret, indulging in regrets, whereas sorry means regretful for an action.

Sorry is also interjection with the meaning: expresses regret, remorse, or sorrow.

Sorry is also noun with the meaning: the act of saying sorry.

check bellow for the other definitions of Regretful and Sorry

Regretful as an adjective:

Full of feelings of regret, indulging in regrets.
Regretful as an adjective:

Sorrowful about what has been lost or done.

Sorry as an adjective (of a person):

Regretful for an action; grieved or saddened, especially by the loss of something or someone.

Examples:

"I am sorry I stepped on your toes. It was an accident."

"I am sorry to hear of your uncle's death."
Sorry as an adjective:

Poor, sad or regrettable.

Examples:

"The storm left his garden in a sorry state."
Sorry as an adjective:

Pathetic and inferior to the point of causing others disgust.

Examples:

"Bob is a sorry excuse for a football player."