Do-gooder (noun)

1. A person who acts in a charitable or helpful way, especially excessively or obtrusively.
2. A person who tries to promote good in the world.

Origin:

Late 19th century: from do-good + -er.

Examples:

1. He was labeled as a do-gooder by his critics.
2. The do-gooders were out in force today.
3. The charity was run by do-gooders who wanted to make a difference.
4. She was labeled as a do-gooder because of her constant volunteering.
5. The do-gooder's actions were seen as condescending.