One word Substitution

1. One who is out to subvert a government 

Anarchist

2. One who is recovering from illness 

Convalescent

3. One who is all powerful 

Omnipotent

4. One who is present everywhere 

Omnipresent

5. One who knows everything 

Omniscient

6. One who is easily deceived 

Gullible

7. One who does not make mistakes 

Infallible

8. One who can do anything for money 

Mercenary

9. One who has no money 

Pauper

10. One who changes sides 

Turncoat

11. One who works for free 

Volunteer

12. One who loves books 

Bibliophile

13. One who can speak two languages 

Bilingual

14. One who loves mankind 

Philanthropist

15. One who hates mankind 

Misanthrope

16. One who looks on the bright side of things 

Optimist

17. One who looks on the dark side of things 

Pessimist

18. One who doubts the existence of god 

Agnostic

19. One who pretends to be what he is not 

Hypocrite

20. One incapable of being tired 

Indefatigable

21. One who helps others Good 

Samaritan

22. One who copies from other writers 

Plagiarist

23. One who hates women 

Misogynist

24. One who knows many languages 

Polyglot

25. One who is fond of sensuous pleasures 

Epicure

26. One who thinks only of himself 

Egoist

27. One who thinks only of welfare of women 

Feminist.

28. One who is indifferent to pleasure or pain 

Stoic

29. One who is quite like a woman 

Effeminate

30. One who has strange habits 

Eccentric

31. One who speaks less 

Reticent

32. One who goes on foot 

Pedestrian

33. One who believes in fate 

Fatalist

34. One who dies without a Will 

Intestate

35. One who always thinks himself to be ill 

Valetudinarian

36. A Government by the people 

Democracy

37. A Government by a king or queen 

Monarchy

38. A Government by the officials 

Bureaucracy

39. A Government by the rich 

Plutocracy

40. A Government by the few 

Oligarchy

41. A Government by the Nobles 

Aristocracy

42. A Government by one 

Autocracy

43. Rule by the mob 

Mobocracy

44. That through which light can pass 

Transparent

45. That through which light cannot pass 

Opaque

46. That through which light can partly pass 

Translucent

47. A sentence whose meaning is unclear 

Ambiguous

48. A place where orphans live 

Orphanage

49. That which cannot be described 

Indescribable

50. That which cannot be imitated 

Inimitable

Even More...