There is special type of illagers called lietuenants, all you need to know in general is that they have above 100hp and may have partial knockback resistance. Here all the lietuenants you may encounter

Lietuenant douglaz:
Is a pillager with OP enchanted crossbow, shoots poison arrows

Lietuenant fredrick:
Is an evoker riding a fast sheep. May have reduced cooldowns

Lietuenant johnny:
This vindicator will attack any non-illagers with increased speed

Lietuenant ketamine:
An illusioner with bow on power X, shoots nausea and darkness arrows. Has 5 armor

Lietuenant xantida:
This pillager will infect random person’s mods with virus. To remove it they have to kill that lietuenant. If someone else kills it he dies. The lietuenant’s drops are somewhat confusing

Lietuenant alzheimer:
This vindicator has ridiculous knockback. Better use netherite armor combined with ranged weapons. He may drop his fortune IV shovel from his inventory.