The only story I have that comes close is the story of Jargo, the angry marine.
Last member of his squad armed with just a flamer. He killed a full squad of necron Deathmarks with his flamer, survived a volley of shots from a full warrior squad, managed to wound a wraith with overwatch which then failed its charge. He then killed the wraith with his flamer and proceeded to charge the other two, surviving two turns in an epic battle.
“Insane? You dare to claim that we are insane? I find this very amusing. You see, there is no such thing as sanity. Why? Because the nature of sanity depends on the context the term is used. A man living in squalor may call the rich man insane for wasting food, while the rich man in return may call the poor insane for living off his waste. You slaughter thousands and squander the resources of planets on foolish incursions to please a corpse and his corrupted followers. And you have the nerve to call me insane? Oh poor misguided individual, pray to whatever deity you serve and hope he is merciful, for those who find themselves trapped in the spiders web have little else they can do”
Lord Nerthro of the ‘Heralds of Absurdity’ to what remained of an Imperial scouting party