Here, your Mega needs to be Charizard as it isn’t reliable enough otherwise. We can see some kind of overlap/anti-synergy between Charizard and Feraligatr. If you pick Mega Charizard Y, the Sun will weaken Fera’s Waterfall. If choosing the standard Charizard X, then both will be Dragon Dance Sweeper. So, in that case, Charizard should be used as a Wallbreaker with Swords Dance. Feraligatr has a higher damage output with a Life Orb and Sheer Force than with it’s Mega. The problem is the speed as any Choice Scarf user will outspeed. I can still make you something good!
Question, is it for competitive battle or adventure?
Feraligatr @ Life Orb
Ability: Sheer Force
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
-Dragon Dance
-Waterfall
-Ice Punch / Crunch
-Crunch / Superpower
Charizard @ Charizardite X
Ability: Blaze
EVs: 40 HP / 252 Atk / 216 Spe
Adamant Nature
-Swords Dance
-Roost
-Flare Blitz
-Dragon Claw / Outrage
Fera: Crunch hit psychic types like Slowbro and Mew, Ice Punch hit Grass and Dragon type such as Garchomp, Lati@s, Amoonguss or Serperior. Superpower targets Ferrothorn, but doesn’t benefit from Sheer Force and thus, does Life Orb recoil. Aqua Jet can out prioritize Talonflame and allow to get Choice Scarf users. It doesn’t get Sheer Force either.
Charizard: the EV spread with Adamant allow to outspeed 252 Spe Kyurem-B with a neutral nature and below. 252 Spe with Jolly will tie with opposing base 100 and outspeed Jolly Excadrill outside sand. However, you loose the power to OHKO Azumarill at +2 after Stealth Rock.