>>55389877>beating all 8 gymsPikachu didn't handle them solo. Others did a lot of the heavy lifting.
I'll compare Pikachu's contributions in the final gym battles of each generation.
Kanto, I'll ignore TR's gimmick battle and use Blaine instead. OS is a mess, as always. Pikachu went from one-shotting Rhydon by aiming for the horn, to failing to even breach Magmar's passive heat brimming off his body. A good and bad showing that can't be measured, typical OS nonsense.
Johto, Kingdra shrugged off several of Pikachu's thunderbolts, and Ash returned them. In their rematch, Pikachu manages to faint Gyrados after Claire gets overconfident and sends it in for a wrap only to get hit with several point blank thunderbolts. Pikachu is knocked out by Dragonair immediately after, failing to land a hit. A decent showing, even for a 4x type advantage, but not on the level of legendaries.
Hoenn, Pikachu ohko'd Seaking with Iron Tail, which looks good, but after that Pikachu struggled to destroy an Ice Ball with a full power thunder, which bought Corphish enough time to finish Sealio off. Still not legendary-tier yet.
Sinnoh, Pikachu struggles to KO Electivire after a lucky Static proc and several lucky Paralysis procs, and does some damage to Luxray before going down. Still not a godslayer.
On Regiice,
Regiice was only recently caught, and even in the games the Regis have fairly low levels. Juan's, the 8th gym leader of Hoenn, had higher levels than the Regis.