Chevrolet Cobalt SS
Although discontinued, the Cobalt SS was one of the best and most powerful four-cylinder cars. Available as a supercharged, turbocharged, or naturally aspirated model, the best SS was the turbocharged 2.0-liter four-cylinder introduced in 2008 (via Autopian).
The engine delivered 260 hp, which was astonishing by the standards of the day and more than any of the competitors. Also, the Cobalt SS had big tuning potential, so it’s relatively easy to get even more power from the engine.