Sasuke's dimension hopping is not instantaneous and takes some time fro him to open it, that time is enough for anyone fast enough to one shot him as he needs to concentrate on opening the portal and is vulnerable during that time, so its not something he can use in battle. Ameno can be countered by Naruto's speed and can be attacked by his shadow clones spread throughout the battlefield covering the area equal to Sasuke's teleportation distance as the radius so wherever he comes out of ameno again he'll be one shotted by a clone.
Someone like Kaguya can let Sasuke travel dimension and then go to his dimension and enjoy her time killing him as he'd still be recharging his Rinnegan. Sasuke can even be killed by techniques like Rasengan if one is able to hit him directly whereas against RSM Naruto such techniques are useless due his healing.
Apart from that if Sasuke uses Susanoo then anyone who can counter it stand a chance to kill him. Like Kaguya, Naruto and DMS Kakashi.
To kill Naruto you need to get rid of his RSM first which would be quite difficult for anyone to do considering the amount of NE chakra. Even Sasuke won't be able to balance Naruto's NE chakra with his own and a full kill intent Naruto would be kind of a berserk fighter. Only Ka genjutus would work against him imo since he won't be aware of it being cast on him apart from that I don't see any genjutsu standing a chance of influencing his massive variety of chakra and controlling it.
Not enough time to open a portal ???
Listen to this : Sasuke uses a Susanoo and then opens a portal and then escapes ...
I already know that Kaguya can kill Sasuke . She is worst opponent for Sasuke ...
Many techs can kill Naruto if hit him ; Ash bones , Indra's arrow , Kamui sphere and ...... And I know that a massive rasen shuriken may be enough to kill Sasuke if it hits him . But he can easily dodge that .
To kill Naruto , you can do all of these :
1-Send him to another dimension : one shots him
2-Use a powerful genjutsu : IT , Tsukuyomi and Kotoamatsukami (,Izanami ??)
3-Attack him with his own technique : using Yata mirror can do so