Il. loud and clear 12. mean and unkind 13. clean and tidy 14. big and strong 15. loving and giving 16. tall and handsome 17. small and expensive 18. nice and warm 19. short and sweet 20. sick and tired

Sure, here are the pairs of words you provided with contrasting adjectives:

12. loud and clear
13. mean and unkind
14. clean and tidy
15. big and strong
16. loving and giving
17. tall and handsome
18. small and expensive
19. nice and warm
20. short and sweet

Let me know if you need help with anything else!