To put it quite simply, the game crashes when I've got only Bountiful and Forgelin in. I am currently using the latest version of Forge for 1.12.2 as well as the latest versions of both mods present.
crash-2020-05-26_21.10.32-client.txt

The crash log explains it pretty well:

Caused by: java.lang.Exception: 'bountiful/rewards.json' contains one or more invalid rewards. Invalid rewards: 
[
PickedEntry (Stack) [Item: dungeontactics:bag_food, Amount: 300, NBT: null, Weight: 100, Stages: null], 
PickedEntry (Stack) [Item: dungeontactics:bag_potion, Amount: 300, NBT: null, Weight: 100, Stages: null], 
PickedEntry (Stack) [Item: dungeontactics:bag_ore, Amount: 800, NBT: null, Weight: 100, Stages: null], 
PickedEntry (Stack) [Item: dungeontactics:bag_tool, Amount: 800, NBT: null, Weight: 100, Stages: null], 
PickedEntry (Stack) [Item: chancecubes:chance_cube, Amount: 1000, NBT: null, Weight: 100, Stages: null]]

Sounds like you downloaded a modpack, then removed Dungeon Tactics and Chance Cubes. The modpack author has configured items from those mods as rewards for bounties. You've got to remove them from config/bountiful/rewards.json or the game will crash 👍

Funny thing is I didn't download a modpack, I got the mod straight out of curse forge, But thanks!

Well, you used a bad configuration file from somewhere else, somehow, which was probably from a modpack containing both of those mods. This mod adds none of those things. This is the list of default bounty data in 1.12, and those items are obviously not things that I would add :^)