I've had a really hard time defeating Malva, the fire-type member of the Elite Four. She had a level sixty-five Talonflame, which was quite difficult to take down. With Brave Bird, it was able to get through Scizor, Blastoise, and Chesnaught—three of the most valuable members of my team. Thanks to Flare Blitz, it was able to defeat Dusknoir and other members of my team. Her Pyroar was hard, too, as well as her Chandelure. They were both able to get many of Pokémon taken down with Wild Charge and Shadow Ball, respectively.
The toughest Gym Leader would have to be Clemont. With the help of a few Aerial Ace from his Emolga, he had the chance to make my Chesnaught faint pretty easily. Emolga has access to Volt Switch, too. Thanks to that, it was able to take down my Wartortle and Espeon within just a blink of an eye. Clemont also had a Heliolisk on his team, which was ten-times harder. It had great Speed, and whenever I tried to alter its status, it would restore itself thanks to Dry Skin. To finally defeat this Gym Leader, I was required to re-challenge him for about four to five times. d: I've managed to land three critical hits when I won, so I guess I was pretty lucky! If it wasn't for those, then it would've taken me even longer to beat him.