I know Matthews is the worst playoff performer ever so this is impossible, but here is a list of worse active players.
Marchand, Couture, ROR, Scheifele, Giroux, Robertson, Kadri, Kopitar, Tkachuk, Backstrom, Zibanajed, Hubeardeau, Panarin, Johansen, Nylander, Tavares, RNH, Barkov, Gaudreau, Duchene, Stone, Hintz, Stamkos, Kuznetsov, Pavelski, Marchessault, Verhaeghe, Benn, Smith, Hall, Barzal, Suzuki, Karlsson, Forsberg, Wheeler, PLD, Hertl, Connor, Laine, Hyman, Oshie, Pacioretty, Tarasenko, Svehcnikov, Caufield, Fiala... and there is much more.