One words substitution: 

1.       Able to use the left hand and right hand equally well - Ambidextrous 

2.      A man who hates marriage - Misogamist

3.      A person who enters without any invitation - Intruder

4.      The words with opposite meanings used together - Oxymoron

5.      A person leaving his native country to settle in another - Emigrant

6.      One who compiles a dictionary - Lexicographer

7.      Too much official formality - Red tapism

8.     One who devotes his life to the welfare and the interests of other people - Altruist

9.      A person who opposes another - Antagonist

10.  A person who does not want to see the realities of life and tries to escape - Escapist