Hello, I am wondering if there are any novels where main character dares to use poison to achieve his purpose and doesn't exactly care about consequences or believe it to be cowards act. For example, to get revenge against some family dares to poison whole city or bunch of innocent people. Most novels I read always had poison just as supplementary method next to cultivating or used only in cases as "eye for eye, tooth for tooth", but I kinda want to read something where it's more than that.
Interesting. Now even I am looking forward to it. Like in fate zero emiya uses any method to kill. I came across such scenarios multiple times in "When A Mage Revolts" awesome novel if you haven't read. To escape from reinforced city, MC curses the city's water. And Almost half of the population die and people scared rush out of the city trampling guards. In another scenario they start fire inside the city to escape outside.
Tales of Herding God. The mc use poison as one of his means and thinks it is very right and proper way.
Go with the classics like "The Deer and the Cauldron". In this book, the protagonist never learns how to fight very well so he resorts to other techniques, often using poisons to defeat his enemies. And he does so in a world where most people regard using poison as dishonorable but he doesn't really care.
Nine Star Hegemon Body Art MC has the memory of an alchemists god, which he uses to make poisons etc. for convenience & extra support in some of his fights & tactics. Sorry, I don't remember much novels atm. I remember that in ATG the MC poisoned millions to death for revenge though, but he doesn't use poison regularly. Both MC's are kind of "shameless" if you look at them when it comes to revenge the will use any means to exterminate their enemies, especially when their reverse scale is touched. So maybe search novels with the series finder with the Alchemy/Antagonist/Shameless Protagonist & Poisons tags might get you some more results too?
Records of The Human Emperor has a similar case. Sure, it's technically not "poison", but "plague" He "only" drives an entire *country* to mass famine with it ;3 The Empress's Gigolo too. He does like spamming his Sarin gas
Falling Star of Evolution MC has knowledge of making poison and uses it daily for battles, killings etc. Not afraid to use it especially in battles with armies involved.