I've spent a week trying to follow the instructions of Aternos Hosting's scare support team, half the time they leave short vague unhelpful responses while waiting for days to hear from an actual competent helper who'll leave lengthy sentences explaining to the best of their ability what the problem actually is.
Aternos Hosting is a free server hosting site, and I've become more aware at the faulty problems that arise from dealing with these sort of sites.
I've ran into one problem after another trying to set up a custom modpack using their 1700MB RAM limit, and their mods/plugins available are limited due to what they actually wanted to go through the effort of testing and putting on their site to share (that and what they got permission to use).
The latest issue is: "I have uninstalled and reinstalled my Minecraft 3 times, completely removing all folders every single time. I don't have Technic installed at all. I don't have any mods in either Aternos Mod Folder or in my .Minecraft folder and I'M STILL GETTING THIS. I literally have reinstalled Forge three times as well, going with the recommended version for 1.7.10 I need someone to tell me what the actual bleepin bleep is going on because I'm beyond exasperated with trying to get a modpack made via testing every single minute detail."
I looked for a solution online and found this: https://minecraft.curseforge.com/forums/general-curseforge/support/241876-jopt-simple-4-5-jar-wont-let-me-launch-any
Following the instructions I had deleted the jopt-simple file in the sf folder and moved the zip folder in there instead, extracting the folder and retried launching the minecraft launcher with the same error.