It's well-known that indiscriminate use of a drug leads to resistance. My question is what the limits on resistance are. It seems obvious that there must be limits: for example I can hardly imagine a tiger evolving "resistance to bullets", and similarly I can hardly imagine a microorganism evolving resistance to heat treatment @ 1000 degrees celsius (surely its proteins must long denature before then).
Are there methods of killing microbes that cannot be resisted? If so, can we make similar cannot-be-resisted drugs?