I assume you mean 'modpack' since if you were after a mod you'd be after modding tools, or crafttweaker along with certain mods I'd guess?
Do you have the necessary cores/libraries/APIs for any of those mods. Always check those types of requirements for mods first.
If it's a mod conflict, sort out what mods are conflicting. It can be tedious to do 1 mod each time to work out what's conflicting, but it makes it easier to tell the issue without having to go into the code or crash reports to work out what's conflicting, especially if more conflicts are the cause than an expected 1 cause. But if the crash reports do make it clear of the cause, take a look at them. Sometimes the E in UE, UCE, UCHE its a clear sign it's an error/mod conflict. If it's something else, like a core/library that's missing it might state it in the crash report in the text detailed, and not as table formatted like the UC, UC, UE state of the mods loading correctly. UC meaning it has loaded that "stage" correctly of course.
I'm taking a look at the mods you have in a pack now to test.
From the look at the mods, some aren't available for 1.8, are they for 1.8.9, or 1.7.10 perhaps?
Also while I'm using Curseforge for adding the mods, some like Orespawn seem off to me, 1.7.10 exist for it on their main website. But I don't know if later versions exist for it since I haven't used it in a while. But mod repost sites (dodgey sites) might have higher versions, but I don't think they are real and more clickbait like those sites are known for.
Make sure to sort your mods by folders (1.7.10, 1.8, 1.8.9, 1.12.2) so that mods don't conflict.