Broken package dependencies

Question

I have seen a lot of questions about similar situations, but no solution suggested have worked for me. I have broken my packages in 18.04 and now I can't uninstall anything to try and start over. I'll walk you though my process.

1. When running sudo apt-get remove --purge gazebo9 I get the output

   You might want to run 'apt --fix-broken install' to correct these.
   The following packages have unmet dependencies:
   gazebo9-plugin-base : Depends: gazebo9 (= 9.9.0-1~bionic)
   ib-sim-plugins : Depends: gazebo9
   ignition-acropolis : Depends: ignition-gazebo
   E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).
   

2. I do what it suggests and run sudo apt --fix-broken install and attempt to install the ignition-gazebo package. Here is the result:

   (Reading database ... 324542 files and directories currently installed.)
   Preparing to unpack .../ignition-gazebo_1.1.0-1~bionic_amd64.deb ...
   Unpacking ignition-gazebo (1.1.0-1~bionic) ...
   dpkg: error processing archive /var/cache/apt/archives/ignition-gazebo_1.1.0-1~bionic_amd64.deb (--unpack):
   trying to overwrite '/usr/bin/ign-gazebo', which is also in package ignition-gazebo2 2.0.0-2~bionic
   Errors were encountered while processing:
   /var/cache/apt/archives/ignition-gazebo_1.1.0-1~bionic_amd64.deb
   E: Sub-process /usr/bin/dpkg returned an error code (1)
   

3. Now I try deleting the /var/cache/apt/archives/ignition-gazebo_1.1.0-1~bionic_amd64.deb file. When I try purging gazebo after this I get the same result as before.

4. Next I try to sudo apt remove --purge ignition-gazebo (which isnt installed so this step was never going to work). This results is the same message as step 1.

I am now left with the puzzle of wanting to remove gazebo (and then all ros-melodic packages which just lead to the same issue) but not being able to because ignition-gazebo is broken and/or missing. Been trying to resolve this absolute mess for 3 days now, does anyone know how to resolve this.

ADDITIONAL: I tried to install the synaptic package so I would have a GUI to do this in, but I can't install it and it gives me the same message as before.