The standard monsters that I could find in the Monster Manual with the ability to cast dispel magic are:
- Death Knight (pg. 47)
- Glabrezu (pg. 58)
- Drider with the spellcasting variant (pg. 120)
- Drow Priestess (pg. 129)
- Lich (pg. 202)
- Mummy Lord (pg. 229)
- Pixie (pg. 253)
- Androsphinx (pg. 281)
- Gynosphinx (pg. 282)
- Mezzoloth (pg. 313)
- Nycaloth (pg. 314)
- Ultroloth (pg. 314)
- And the standard NPC Priest in Appendix B (pg. 348)
Most of these are the kind of monster that would almost certainly attack the party. The NPC Priest might not, but I can't see a reason for a priest to randomly dispel someone's shelter then walk away (unless their god has strong objections to that specific spell, but that seems forced). The sphinxes also don't tend to attack people, but they're rare, completely level-inappropriate, and don't move around much.
The only one of those monsters that I can see randomly dispelling but not attacking is the Pixie. If you read their lore, you can see that they love to troll people without any hostile intent, so this sort of thing is right in their wheelhouse. It also appears to suit your other requirements (easy to kill if it comes to a fight).
First, there are no lists of punishments in the rules.
Second, the default D&D 5e setting is a fantasy medieval one, as such, imprisonment is an inappropriate punishment. Imprisonment as a punishment is a late modern development from the early 19th century:
The original purpose of confining a person within a prison was not to punish them, but was a means of keeping the perpetrator of a crime detained until the actual punishment could be carried out. This was usually in the form of corporal punishment that was intended to cause the guilty person pain, such as being beaten with a whip, or capital punishment which used a variety of methods to claim the lives of condemned individuals.
www.crimemuseum.org
A more appropriate punishment might be the pillory or stocks both of which were used to restrain the criminal in a painful position (Exhaustion might be an appropriated D&D mechanical outcome) and to allow the populace to humiliate them by laughing, hurling insults, rotten vegetables, offal and, of course, human or animal excrement.
Here is an interesting list of historical punishments for both criminals and children from around the world. I give thanks every day I was not an Aztec child.
This presuposes that the rule of law is suficiently established that a common assault is a matter for local law enforcement. In medieval times (and some places today) retribution was a private matter. For example, gathering a bunch of friends together and beating the snot out of the perpetrator.
Best Answer
The Legendary Tarrasque for one
From the MM (286):
Swallow and Bite
The name of the attack you'd be looking for in the D&D 5E Monster Manual is Swallow. The Giant Frog (MM 325) and Giant Toad (MM 329) also both have this attack.
Sometimes creatures of the Gargantuan size can swallow their opponents as part of another attack. For example the Kraken (MM 197):
Some others:
That's all of them in the Monster Manual that I know of from flipping through.
Engulf
The Gelatinous Cube has been around since the earliest days of D&D and is a staple of D&D dungeons, tales and jokes. It has a a different method of consuming opponents (MM 242):
The Shambling Mound (MM 270) also has an Engulf action as does the Water Elemental.
Homebrewing a Swallow or Engulf Action
Some main points you'd want to note for a homebrew are: