I don’t agree with you on that… There’s more purpose in the mc’s existence than killing the protagonist. Like he could do whatever he wants since he has the power, world domination and many other goals to achieve…. Only when his existence is all based on killing the protagonist that it becomes boring because once he achieves that, he loses his sense of existence and the story becomes bland.

i don't know if i remember correctly as it has been a while since I read nano machine but it is able to copy and analyse moved so it's just basically giving mc moves to the protagonist for free. also what if that protagonist comes to kill mc would he be helpless then? i haven't started reading yet so idk

You’re right… the nano machine has the ability copy and analyze moves, but the mc might not be able to use them if he does not have the force qi to perform it, i.e demonic force qi or ice force qi. (But he can analyze it to search for the weaknesses or use it as a reference to create a new martial art) but it’s not possible for the mc to be helpless before the protagonist, the mc has ‘divine talent’ which means he can analyze martial arts too and create one easily, infact the talent is beyond comprehension. So as the nano machine copies and analyze hus moves, he is doing so too and to everyone. the rule of not killing the protagonist just makes things interesting.…

if you read nano machine you would no nothing that cripple the mc only if you kill him