Responsibilities vs. accomplishments on your resume

On your resume, is your experience listing responsibilities or accomplishments?

"Reviewed pull requests and code for ensuring quality and test coverage" is a responsibility, that's expected.

"Migrated a 1MM+ line React app"  is an accomplishment.

The next step is going a step further: so what?

• What did migrating the app enable that wasn't there before?
• How did it deliver business value?
• Did you migrate it by yourself or on a team? If the latter, what was your specific contribution?

Cheers,
Kamran