I’d be curious to know how intense you could get using biologically possible/vaguely-plausible reactants and containment structures…
At least in common depiction, dragon fire isn’t just some ignited methane spurted in your general direction, it’s a baleful all-consuming inferno that inflicts horrific damage and burns the flesh down to the bone(depictions seem to vary on effect on metal, from ‘actively showing heroic knights deflecting with their shield’ to ‘doesn’t melt it; but metal conducts heat just fine’ to ‘knight, melty’).
