This will reset ALL settings. Make sure you back up your binds and other custom settings before you do this.
These steps are no longer required to install mastercomfig, but is kept here to document how to completely reset TF2.
If you want to remove your config, delete any configs you may have in
tf/custom and delete the
tf/cfg folder. Then verify your game files using Steam.
Next, if you have Steam Cloud Synchronization enabled, make all the files in
STEAM_FOLDER/userdata/USER_ID/440/remote/cfg blank. Do not delete them, or else Steam Cloud will redownload them. Alternatively, you can disable Steam Cloud.
Finally, launch TF2 with only the
-novid -autoconfig -default +host_writeconfig config.cfg full +mat_savechanges +quit launch options. The game will launch and exit. Afterwards, remove these launch options.