Qiaochu Yuan already mentioned in a comment Kronecker's negative impact on Cantor's first paper on set theory which was ahead of its time about 20 years, when published in 1874, and which had been delayed several months, unusually long (for that time) such that Cantor considered to withdraw it. Über eine Eigenschaft des Inbegriffes aller reellen algebraischen Zahlen. Crelles Journal f. Mathematik Bd. 77, S. 258 - 262 (1874).

But it is less well known that Cantor's paper PRINCIPIEN EINER THEORIE DER ORDNUNGSTYPEN, ERSTE MITTHEILUNG had to be withdrawn from Mittag-Leffler's Acta in 1884 and had to wait for publication until Ivor Grattan-Guinness published it in Acta Mathematica 124 (1970) 65 - 107. This paper contains a tremendous richness of proposed applications of set theory. Its enforced withdrawal seems to have given Cantor the first really hard stroke.