Blew my arduino pro mini s4 named component
Many Arduinos have a Schottky diode between the power connector and the voltage regulator as a protection against accidental reverse polarity connection. The official Pro Mini, or the Sparkfun variant, does not.
So you can either de-solder the diode or break it off the board using diagonal cutters and then replace it with either a similar diode -- or with a solder-bridge if you are confident about never connecting power the wrong way around.
It's possible (likely even) that other components that look OK visually are actually damaged. Especially if you can't power the board by connecting a regulated 5V supply to the VCC pin.