Having the same issue as well. I've done everything I can think of, besides uninstalling and reinstalling.

Can you provide system specs? And I believe someone had success after force-verifying their Stellaris installation.

Getting the error log and crash report would be useful too. Should be in this folder:

C:\Users\[YOUR NAME]\Documents\Paradox Interactive\Stellaris\crashes

I had the same problem. (I mean it crashed on reaching 100% on starting the game)

What fixed it for me, was removing my custom empires. There is a file in the C:\Users\[YOUR NAME]\Documents\Paradox Interactive\Stellaris directory called "user_empire_design.txt" if you want to keep them.

Interesting, Michael!

If someone could share a copy of that file that's breaking the game loading, I might be able to raise it appropriately with PDS.

In my case I believe it was custom empires including mod content. In this case from the error.log:

[20:13:02][empire_design.cpp:484]: invalid planet class pc_pd_mesa. file: user_empire_designs_v3.4.txt line: 1045.

Hmm, if you have the full file though, that'd be super helpful. :)

[20:09:11][dlc.cpp:337]: Invalid supported_version in file: mod/ugc_1506078758.mod line: 9
[20:09:11][dlc.cpp:337]: Invalid supported_version in file: mod/ugc_2032118923.mod line: 8
[20:09:11][dlc.cpp:337]: Invalid supported_version in file: mod/ugc_3160784590.mod line: 8
[20:09:11][dlc.cpp:337]: Invalid supported_version in file: mod/ugc_3245080043.mod line: 13
[20:09:24][bitmapfont.cpp:3499]: Could not find coloring for character 'Y' (0x59)
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_fusion_array.txt line : 28. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_fusion_array.txt line : 29. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_fusion_array.txt line : 30. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_fusion_array.txt line : 31. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_fusion_array.txt line : 32. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 29. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 30. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 31. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 32. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 33. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 34. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 35. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 36. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 37. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 38. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 40. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 41. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 42. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 43. Got country
[20:13:01][trigger.cpp:627]: Invalid Scope type for trigger planet in common/megastructures/STNC_particle_fountain.txt line : 44. Got country
[20:13:02][empire_design.cpp:484]: invalid planet class pc_pd_mesa. file: user_empire_designs_v3.4.txt line: 1045.
[20:13:04][prescripted_systems.cpp:953]: There are no initializers with [usage = fallen_empire_init]. Game won't be able to generate fallen empires
[20:13:13][game_util.cpp:398]: Failed to register used portrait in gamestate: portrait 'synth_machine_07' for the class 'MACHINE' is not found in portrait set database

This is the full error.log.
For the "user_empire_designs_v3.4.txt"-file It's over a thousand lines long, so I can't really paste it here. Edit: But it seems to just have the definitions for the custom empires I had created.

Perhaps on the Discord? Sorry appreciate it's a hassle but if I can get something reproducible to Paradox they may be able to fix it and that'd be a win for all mods that might have the same issue. :)

I posted a bug report on the Renegades M.G. Community Discord under STNC_bug_reports. The bug report is titled "Stellaris Crashes when at 100% of Loading the Mod" and I have the same display name and avatar on discord for reference. In the bug report, I posted the files from my most recent crash. The files include "exception", "settings", "error", and "system". Let me know if any other files would be helpful so the issue can be tracked down. It does look form the error report that the crash is caused by something interacting with the custom vanilla empires, which was never an issue before. Thank you for the help and your responsiveness when dealing with bugs. Thanks

Okay, there's a good chance this may be resolved now.

The problem appears to be fixed now. Thank you for the help in resolving the issue

The mod just doesn't load for me. The game loads into the regular Stellaris game with no sign of the mod, and yes, it is correctly added to the playset. There is no crash in my case. Are there dependencies that I have to download?

I fixed it. I had to add this to the end of the .mod file in the stellaris "mod" folder: path="C:/Users/USERNAME/Documents/Paradox Interactive/Stellaris/mod/MODFOLDERNAME"

Dang this game has a lot of species. Borg "Cooperative." Neato!

That's weird...

Same. The mod just doesn't load for me. All the same details as Train me. I am not sure how to add Train me's fix to the .mod.