1. Visible – invisible

2. Successful – unsuccessful

3. Practical – impractical

4. Patient – impatient

5. Reliable – unreliable

6. Regular – irregular

7. Social – antisocial

8. Attach – detach

9. Respect – disrespect

10. Exhale – inhale

11. Possible – Impossible

12. Cooked – uncooked

13. Introvert – extrovert

14. Voluntary – involuntary

15. Responsible – irresponsible

16. Do – undo

17. Important – unimportant

18. Precise – Imprecise

19. Shaven – unshaven

20. Predictable – unpredictable