Mobs have been scaled to be significantly more difficult. Accordingly, their drops have been increased to make slaying them more rewarding.
These changes are all server-side only, as such a client-side mod is not needed.

Zombies:

Odds and quality for armor and tools have been drastically increased

Spiders and Cave Spiders:

All spiders now give poison, cave spiders now give wither

Drowned:

Guaranteed to have a trident or nautilus shell
Drastically increased chance of dropping trident

Piglin:

Natural spawns are often replaced with Piglin Brutes

Ghasts:

Health tripled
Shoot up to 3 fireballs at once

Blazes:

Deal thorns damage while their fire is active
Deal double damage to shields

Creepers:

On explosion spread a lingering potion of some kind
Small chance to spawn charged
Even smaller chance to spawn invisible

Warden:

Immortal
Will ignore noise from redstone equipment

Zoglin:

Double Health
Take half damage

Drop Upgrades:

All Hostile:

The quantity of their normal drops have at least doubled when killed by a player
Have at least a 1 in 200 chance to drop a totem of undying (except endermites)

Piglin Brutes:

Chance to drop an ancient debris

The following mobs have a new garunteed drop:

Elder guardian, Ravanger, Zoglin, and Skeleton Horse: 1 totem
Evoker: 2 totems
Ender Dragon and Wither: 9 Totems

Toxxic Mob Scaling