>>54530929People meme about Alakazam getting hurt by it but honestly losing the elemental punches for Shadow Ball and Focus Miss is absolutely a fantastic trade-off.
The biggest losers, generally speaking, were specialized tanks. Part of what made Blissey and Skarm so good was that they'd practically never have to absorb SE damage tanking their respective damage types. The split changed that and made both less reliable as a result, as well as severely hurting more niche tanks that could somewhat get by thanks to predictable damage types (Articuno, Regice, any Rock/Ground)
As for offensive threats, Sceptile was probably the biggest loser since it was designed specifically around pre-split move distribution.