If you have not tried this already, move all the files / folders in the system/user/addons directory somewhere else and try opening your control panel. Removing the files from the addons directory prevents EE from loading these addons, and so while you may get some errors arising because it cannot find the addons it is looking for, you eliminate errors caused by incompatibilities in the add-ons found in that folder.
EE changed how addons work between EE2 and EE3, so EE2 addons will not work in EE3. Unfortunately, although EE could easily test for EE3 compatibility and not load those that are not compatible, it doesn't do this and attempts to load anything it finds in that directory: if there are issues of compatibility you find out via opaque errors instead. That seems to be what is happening in your current circumstance.
If you can get the EE CP to load with no add-ons in the addons folder, then start adding them back one at a time and see how you go - if you add one back and EE crashes, you know that there is an issue with that add-on and you'll have to fix it or work around it.
If you post a list of whatever addons you have in the addons folder under EE2, it will be possible to reply with whether or not there are EE3 compatible versions and so on.