In any pokémon that you eat, it is necessary to remove the toxic or unsanitary organs. Some are universal, but you must also approach each corpse with its own unique challenges. For example, poison types, of course, have many glands throughout their bodies you must remove immediately before they can contaminate the good meat.
NOTE: UNDER NO CIRCUMSTANCE SHOULD YOU EVER EAT, KILL, FIGHT, OR HARM A SEVIPER.
While most any pokémon you kill will, at least at first, look like a charizard, you should not expect them to fight or react like one. They will invariably attack from limbs that they shouldn't have, with moves it does not make sense that they could learn. Pay attention to how they move, as their horribly unnatural stature betrays their true species. If their stomach rips open to spray you with acid, for example, you can comfortably assume they are not truly a fire type.
Note on agitation: The pseudo-zards will consistently and repeatedly call you a coward, abusive, a terrible friend, etc.. Even after their bodies go limp, they will continue to judge you harshly. Use their mockery as a reminder to why you are here. It is tempting to let them get under your skin and use the anger to fuel a murderous blood rage, and while that is certainly tempting, even necessary, you must understand that life is absolutely precious. You are not killing to satiate revenge, but hunger.
Their mockery, of course, is for your betterment. You must listen to them and internalize their message. You must understand yourself as useless, worthless, and mindless. You are nothing more than a wild pokémon. You are here because you left society behind. Let the charizards remind you why you left. It is not their failing, but yours. You were unable to better yourself or work out your flaws and aggression in ways that would not harm others. You left because every attempt at satiating your pain left you consuming toxic and disgusting behavior in a misguided attempt to ruin the lives around you so that yours would seem bearable in comparison.
You are nothing more than a wild pokémon. Let The Dungeon take care of you, as it does everyone else. Leave your worries to The Dungeon. The Dungeon will care for you.