Created a modpack on 1.14.3 on twitch with forge 27.0.52, added the few mods i wanted just like any other modpack but when i go to start the pack i can choose my installation and all that but once i hit play, it immediately crashes with no report at all, it just says something went wrong. On top of that, i tried to create a server for my friend and i to play on with the same new modpack, and it wont start as soon as i add mods, it ran previously to me adding mods. https://pastebin.com/THBXbV3h crash report for the server. The thing that i can't figure out is that i've quadruple checked with my friends and i'm not missing nor do i have too many mods on the server or on my personal modpack, ours are clones but he can run his perfectly and play singleplayer no problems.
From my experience with software looking at those exceptions makes me think you have an issue with an incorrectly installed mod or something like that. It keeps trying to find a class or get an Instance of a class but fails on that.
This exception feels like it would be the one I would look into more:
Attempted to load class net/minecraft/client/settings/KeyBinding for invalid dist DEDICATED_SERVER
And a quick search for net/minecraft/client/settings/KeyBinding resulted in this post
I would link a list of the mods you have in the modpack so that the people who have knowledge of mods can help you pick out ones that are causing the issue