you probably went on with terminal and typed something like:
sudo apt-get install libsdl2-dev
You can reverse the install of every install you make by editing the code:
sudo apt-get remove libsdl2-dev and purging it with --purge, then it looks like:
sudo apt-get remove --purge libsdl2-dev
Your terminal has a history, so every command you entered lately can be found by pressing the UP key, find what you installed and change the code to remove/purge it.
EDIT: Run the whole command in terminal to clean up.
echo "Cleaning Up" &&
sudo apt-get -f install &&
sudo apt-get autoremove &&
sudo apt-get -y autoclean &&
sudo apt-get -y clean
After that you can check the residual files in Synaptic Package Manager,
referring you to this LINK