Curse mark was super dangerous.I can think of several instances he almost died because it paralyzed him.plus he was thoroughly explained the price of having cm2.the curse mark consumes you over time and you'll lose your freedom.plus he had to go into a coma.
For ems sasuke had to fight itachi with everything he had.he was so tired after the fight he slept a couple days.if fighting itachi for ems is a free powerup,what does that make kcm/bm?
And if you say itachi "went easy",consider the fact that naruto had unlimited sage mode and his mom to use her slave chains...seriously who lets their mom fight their battles?
Because Sasuke can use them without any training and gain them without any training. People say the same thing about Naruto having Kurama because Minato gave him them even thought he can't use the power whenever he wants since Kurama can take over him, his seal weakens, the chakra cloak actually hurts him and when it heals Naruto it shortens his life. Sasuke did have pain using his CM but that's because he was told not to use it and he was trying not to use it and it paralyzed him when he was either trying not to use it or after Kakashi sealed it. When Sasuke start to use his CM he gain use of it without any training and he even used a pill which increased his base stats.
Sasuke didn't fight Itachi for EMS, it was for MS since Obito said Itachi plan the fight so he would die by Sasuke's hands while also planning to rid Sasuek of Orochimaru and the CM. Sasuke did nothing to get Itachi's eye since he wasn't fighting for that reason nor did he earn them in an actually fight. Sasuke wasn't fighting to gain anything, he wanted revenge and he wouldn't even know about the MS or EMS without Itachi telling him about them so Itachi is the reason Sasuke got them.
Naruto was fighting the strongest Bijuu, him having help fighting Kurama is actually understandable while Itachi was sick and still planned the whole fight. Also Kushina first stopped Kurama so she can talk to Naruto then she only tripped Kurama when Naruto attacked so it wasn't like she was fighting the whole fight with him as he was still the one to pull Kurama's chakra then he had to actually train to use that chakra and didn't have the power and use it freely.
P.S. I don't care if they were given or borrowed, I only don't like it when they can use a power well with no training at all. Same goes for BSM, Naruto had incomplete training of KM then gets BM and BSM. I rather Naruto and Sasuke train in their respective powerup so we can get a better fight.
