There are some cases when there are some users with IDs like user1231** who keep posting bad questions knowingly again and again.
Does the community have the power to delete or suspend such accounts? If yes then what is the way to do it?
New accounts that post a series of extremely poor questions that aren't spam will soon find themselves without the ability to post questions in the future. This is an automatic process that can't be lifted (or levied manually) by moderators. Sometimes, we do place users in timed suspensions for low quality contributions over time in an effort to slow them down before they hit the automatic ban.
Accounts that post convenient links for our users to buy Gucci bags cheap are destroyed by moderators, just flag the SPAM and we'll launch missiles once we confirm it.
Just keep in mind, SPAM is blatant unsolicited advertising. Horrible questions are just horrible questions, an issue of quality - not abuse.
If their contributions are bad enough, a post-ban will kick in automatically. Exactly what causes this to happen or when it happens is a closely guarded secret not even moderators are aware of. Have a look through the post-ban tag here on Meta for some interesting material.
When this occurs, such users will be directed to: What can I do when getting "We are no longer accepting questions/answers from this account"?
It explains to them why the ban might have happened and what they can do to have it automatically lifted.