You may be going for the word expatriate.
The opposite of merciful using a prefix is merciless.
Disobedience
unpleasant
The opposite of sever is conjoin.
Anti-social.
The prefix 'dis-' is used in this sense as 'to do the opposite of', as in 'disallow'. To disconnect, therefore, is to act in the directly opposite of 'connect'.
Construct
The opposite prefix of the prefix "meta-" is "pre-".
Hypo is the opposite of the prefix hyper.
The opposite of detach using the prefix ad would be "attach", meaning to connect or fasten something to something else.
May be "split",yea
There is no opposite of particular using a prefix (a- or im- or in-). The term "in particular" is an adjective or adverb phrase.