Green’s Dictionary of Slang

(US) to the greatest extent, extremely, very badly.

1839		Marryat Diary in America 1 Ser. II 227: He loves Sal, the worst kind [DA].
1848		Bartlett Dict. Americanisms 517: Worst Kind. Used in such phrases as, ‘I gave him the worst kind of a licking.’ [DA].
1893		W.K. Post Harvard Stories 140: Then he begged worse kind just to let him look out of a window where he could see you.
1904		N.-Y. Trib. 26 June n.p.: ‘So you want to go to Cuba, do you?’ asked Colonel Roosevelt. ‘I do, worst kind.’ [DA].