At least one of your mods requires a later Forge version than the recommended and they have not indicated so in their mod file, so Forge can't catch it and make a proper error screen
1.8.9 is no longer supported on this forum due to its age.
Please update to a modern version of Minecraft to receive support.
Also: You CAN have more than one Forge
Forge installs itself as a version of Minecraft.
Make a new Profile/Installation and select Forge from the version dropdown.
(Note: For some reason Forge 1.12.2 gets booted to the bottom of the list.)