I was playing a match in versus mode with an electric deck. I had my Ampharos EX use Sparkling Tail onto my opponent's Pressure Lugia (which is weak to electric). As stated, Sparkling Tail ignored the weakness, but what it didn't ignore was pressure, which allowed my opponent to win the game. There was no stadium in play, and no tool cards or special energy (excluding double colorless) either.
I'll list the text of Pressure and Sparkling Tail here.
As long as this Pokémon is your Active Pokémon, any damage done by attacks from your opponent's Active Pokémon is reduced by 20 (before applying Weakness and Resistance).
Attack Sparkling Tail
This attack's damage isn't affected by Weakness, Resistance, or any other effects on your opponent's active Pokémon.