1.
You use ~ after a superlative such as ‘best’ or ‘worst’ to emphasize that something is extreme in some way.
...their imprisonment under some of the most horrible circumstances ~...
= conceivable
ADJ: adj-superl n ADJ, adj-superl ADJ n emphasis
2.
You use ~ after a word like ‘every’ or ‘all’ to emphasize that you are talking about all the possible examples of something. You use ~ after ‘no’ to emphasize that something does not have the quality mentioned.
Parents encourage every activity ~.
= possible
ADJ: ADJ n, n ADJ emphasis