This guide will provide you with 15 mobs that could be added to Minecraft.
Dungeons Mobs

Dungeons add a wide variety of new hostile mobs, along with spooky, ethereal, and enchanted enemies.
Monsters

These are regular monsters with a purple glow. They possess strange powers and abilities, ranging from faster movement and double damage to life steal or bursts of electricity similar to charged creepers.
Pink Slime

The corrupted cauldron boss only spawns pink slimes, and the corrupted cauldron itself may not fit well into regular Minecraft.
Traveling Merchants

Minecraft already features a well-known traveling merchant, but in Dungeons, you can obtain rare gear from the luxury merchant.
Wandering Trader

Imagine a rarer version of the wandering trader that offers rare and valuable loot based on your level.
Mystery Merchant

Anything would be better than what you can get currently, and alongside the luxury merchant, there is also the mystery merchant.
Looting Trader

A trader that provides crates containing random themed loot.
Baby Zombie Towers

Baby zombie towers could exist in Minecraft as a new challenge.
Ancient Mobs

Ancient mobs can be found in special end-game quests and drop rare and powerful gear and loot.
Iron Golem

While you can already summon iron golems and tame wolves, it would be interesting to tame bats and bees like in Dungeons. Imagine running around your world with an army of bees. The soul entity is another summonable companion in Dungeons.
Soul Lantern

You can spawn them by using souls on a soul lantern. For example, after killing a vex, you could obtain its soul and use it on a soul lantern to spawn a friendly vex.
Villagers

Dungeons also feature several new villagers. These include the enchanter, who buffs other villagers, the geomancer, who builds walls and places bombs, and the icologer, also known as the chillager, who attacks players with icy effects.
Chillager

The chillager would work well with a frostbite mechanic and could spawn only during snowy village raids for added difficulty.
Wraith

Wraiths are blue ghost-like mobs that spawn fire beneath players. They could spawn naturally in End cities or alongside phantoms to make late-game encounters more difficult.
Patrol Captain

In Minecraft, patrol captains are fairly weak, but in Dungeons, they are armored enemies that hit much harder. Patrols can also wield axes instead of bows, and a rare vindicator patrol led by a powerful captain would be a strong addition.