Modpack Impossible Craft (YT) by OnMod

Hard Edition: Adds twenty mods (plus some other dependencies, etc) that aim to make Minecraft more challenging. This is the lightest, and most vanilla friendly edition. Choose this edition if you want to spice up how you play Minecraft, but do not want to make it significantly harder or different from the base game.

Impossible Edition: Adds many, many mods, most of which make Minecraft harder in some way. WARNING: the mods added make surviving Minecraft much more challenging. The early game is brutal, mobs are everywhere, and progression is difficult. Also, due to the large amount of mods in this edition, allocate more ram if you can and keep in mind it might not run well on a potato. 

You can find the different edition types in the files tab.

Relevant for the Impossible Edition of this modpack:

Goals: Survive. The Early game of this modpack is brutal. Getting basic tools is time consuming and when night falls things get bad really fast. My best advice is to take your time, and get used to spending your first half a dozen nights in hole in the ground. Also keep tabs on your body temperature, thirst levels, stamina, and overall health. Keep in mind that you don't heal normally, you need to make bandages or plaster to heal any injuries you sustain. 

If you somehow survive the early game, mid game will be a bit easier. You need to get a stable food source, stockpile bandages and plaster, mine for iron, diamond, then netherite. Upgrade your gear as mush as you can. 

In the late game you have three bosses to defeat: the Ender Dragon, the Wither, and the Witherstorm. The Witherstorm is the hardest, and should be fought last. However, the Ender Dragon and Wither are not a piece of cake. Thanks to a few mods, taking them down will be quite a challenge.

How to Beat the modpack: Defeat the Ender Dragon, Wither, and Witherstorm and survive a minimum of 100 days, all in Hardcore.