I'm looking for novels where MC develops his power - not just his individual and territory/knigdom/empire by making use of his modern knowledge or some other cheats. I've been reading lots of transmigration where MC get reborn/transmigrate to a prince or noble in ancient time and slowly/rapidly improves his power. But it frustrates me to no end as MC always spare his enemies whom attempts to kill him just cause they're a women & beauty, relative or some random reason. I would like a decisive but intelligent, not a metal who kills everything.
Hmm... Basically it meant that harem shouldn't be involved. How about; Reverend Insanity The Legendary Mechanic The King of the Battlefield I am the Monarch
You should try a different setting... with a prince/noblity setting. If you want MC like that in this setting look for evil MC, abandoned MC, evil power like necromancy so he needs to kill everyone who knows about his secrets etc... But if you don't rlly care for that setting then go for slave mc, poor mc, revenge etc. It's easier to find something like that. For example Warlock of the Magus World and similar.