I’m trying to remove the Hue Bridge from SmartThings, and every time I try, the app just gives me an error and it doesn’t remove. I also tried from the graph.api site, but get an error there too. I just want the lights out of my ST hub and device list, I don’t really mind how that happens.
You will not succeed because they will be found and added back by ST’s LAN Connect. But to remove the hue bridge, you would most likely need to remove all the hue lights first, then the hue bridge. Which brings us back to them being added back automatically. 
Yeah, that’s been my experience so far… I was trying to remove the lights, and then found that they “helpfully” added themselves back. So it sounds like I need to break the connection first, remove all the lights, and then remove the Hue Bridge?
I would not waste my time because ST will simply repopulate the hue bridge and lights since they are on the same network.
Amazingly, this continues to be a problem years after first being raised, so I thought I’d post my solution here to force delete a Hue Hub LAN device. Trying to delete through the IDE didn’t work no matter what I did, and deleting the individual Hue devices would just cause them to be recreated within a few seconds of being deleted.
The solution is to ‘edit’ the Hue Hub device from the IDE, and change the device type to anything else other than Hue Hub (I also changed the name & network ID, but don’t think this mattered).
Once the device type is changed, you can delete it, and in one fell swoop all of the stubborn Hue devices are removed as well.