Despite the blatant favoritism that Pokémon often shows Charizard, its pre-evolved form, Charmander, should never be given to trainers at the outset of their journey. Not because the first two Gyms in Kanto are Rock and Water-types, though that does make it harder to make progress. There's a much more sobering reason Charmander is an awful choice for a starter Pokémon. Charmander is a Fire-type with a small flame burning at the end of its tail -- and if that flame goes out, the Pokémon will die.
When a child turns 10, they are given what's known as a starter Pokémon to begin their journey. For Charmander, more so than any other Pokémon, its life is in its trainer's hands. A light breeze, some rain, an errant Pokémon attack, or even just Charmander not paying attention and accidentally putting its tail down in a puddle... this Pokémon spends its entire life a moment away from death. Charmander requires around-the-clock attention comparable to a human infant, and 10-year-olds are famously not given babies to travel the world with unsupervised.
Unfortunately, not all trainers are as wholesome and dedicated to their Pokémon as Ash Ketchum. Take, for example, Ash's own experience with his Charmander. The Pokémon's previous trainer abandoned it in the forest because it was weak, causing the Charmander to be caught in a heavy rainstorm. It was forced to cover itself with a single leaf in one of the most heartbreaking images in all of Pokémon. If Ash, Brock, and Misty hadn't found it when they did, it surely would have perished.
Upon hearing his Charmander had nearly died in the rain waiting for him, its trainer, Damian, was still not concerned for his Pokémon's well-being. That the Charmander survived for as long as it did borders on miraculous. Clearly, not everyone deserves a Pokémon, yet turning 10 years old appears to be the only requirement. As a Pokémon that's a hairsbreadth away from death at all times, Charmander is proof that a trainer's irresponsibility can lead to tragedy.
In no way, shape, or form should Charmander be considered the perfect partner for a trainer to start their journey with. If anything, a Charmander should only be given to talented trainers who have proven themselves to be trustworthy and responsible. The beginning of Ash's journey made it painfully obvious that rookie trainers are going to make mistakes, and in Charmander's case, a trainer's mistake could cost the Pokémon its life.
Ash would hate to hear this, but sometimes evolving a Pokémon actually is in its best interest. Charmander should always be hastily evolved because the anime later confirmed that if a Charizard's flame goes out, while it will never be able to battle again, it at least won't die. Pokémon battles are inherently violent, but the physical toll on most Pokémon is highly treatable and free of long-lasting effects. Charmander, on the other hand, is always one Hydro Pump away from its demise.