Rantanen helped start a strong comeback from Finland in the third period with a power-play tally, but the Finns could not tie up the game and force overtime despite recording 11 shots on goal in the frame.
The Nousiainen, Finland, native served as an alternate captain for his country and finished the tournament with 11 points (five goals, six assists) in eight games played, tied for the sixth most points at the 2018 Worlds.
For Switzerland, Andrighetto finished the contest with a plus-1 rating in 12:41 of ice time. He was on Switzerland's second line with Timo Meier (San Jose Sharks) and Joel Vermin.
Moving on to the semifinals, Switzerland will take on Team Canada in Copenhagen on Saturday.