That 5.15GB "Other" folder? That's how much space HTC thinks their <1GB OS needs. That 1.01GB of Apps? They are all the Stock Preloaded apps... That you can't remove... or move to the other partition on the inbuilt phone storage.
But that's not that bad...
Yeah... it actually is.
The kicker is that even if I could get all the apps of the phone... it will still show the message because the Phone's Reserved OS space is so large that it will trigger it by itself.
As a stopgap fix, just disable Fast boot. Drops it by *just* enough to not trigger it.
At least HTC left the Bootloader for the One X unlocked... so I could very easily replace the OS... with one less shit.
And given it's out of warranty... I wouldn't lose anything.
And I can even build my own variant from the Official Source code... for my phone.