Unfortunately, you will probably experience a spike at Clair then a big one at Lance. That's the problem with GSC that HGSS did not fix, was the pacing being so uneven. A lot of Johto is sleepwalking through easy routes and Gym Leaders like Pryce and Chuck (who I'll come back to) then randomly facing a boss like Lance who is hard for all the wrong reasons, because you don't have the resources to beat him fair, not because of some amazing strategy on his part.
Back to Chuck, on the topic of this thread I nominate him as the worst Gym Leader in the series. Being the 5th Gym in his region, to only have two Pokémon neither of which are native to his region, is pathetic. I mainly focused on higher stakes Champion fights in my original post but I consider Chuck the worst Gym, and quite possibly the worst overall boss fight in the series. Though Rocket Executives Petrel and Proton from the same game are serious contenders as well.
Zinzolin from B2W2 is also really bad. Really silly name and outfit in my opinion, along with using the Sinnoh native Weavile as his ace when Cyrus already did this in DPPt.