This is a medium-sized modpack whose goal is to make the minecraft game as difficult as possible.

If it's still too easy for you, I recommend installing Epic Siege mod

Modpack adds:
Desire.
Sanity.

temperature
Dynamic weather, tornadoes and natural disasters.
New animals
New biomes.
Stronger monsters.
hard stone layer.

Air pollution.

More weapons.

Seasons

New world generator
and more ...

Mods used:

A Crude Start

Advanced Chimneys

Animania

Antique Atlas

Athenaeum

AtomicStryker's Infernal Mobs

AutoRegLib

Better Foliage

Better Survival mod

BetterFps

Biomes O' Plenty

Bloodmoon

Carry On

Champions

Classic Bars

CoroUtil

CraftStudio API

CXLibrary

Dropt

Dynamic Surroundings

Dynamic Trees

Dynamic Trees - Biomes O' Plenty Compat

Eat the Eggs!

EnhancedVisuals

Farseek

FoamFix

ForgeEndertech

Gases Framework

General Disasters

Glenn's Gases

Hardcore Darkness

Iberia

Just Enough Items (JEI)

Just Enough Resources (JER)

LibraryEx

Mantle

More Furnaces

Multi Mob Library

OreLib

Patchouli

Pollution of the Realms

Primitive Mobs

Realistic Item Drops

Rough Mobs 2

SchopCraft

Shadowfacts' Forgelin

SmithsCore

Spartan Shields

Spartan Weaponry

Weather, Storms & Tornadoes

Zombie Awareness

MRSM - Realistic Survival Modpack