Hunter x Hunter (2011), Kimetsu no Yaiba Recommendations
1- The MCs are optimists + after some training, they become VERY strong
2- Good Action
3- Adventure Gore Action Group of friends
4- Both MCs are on an adventure with a partner and are looking for something
5- Both MCs have huge potential and are extremely strong
Although this show is fairly new, even the Hunter x Hunter mangaka (Togashi) recommended reading the Kimetsu no Yaiba manga series. The anime adaptation has been great so far and as a huge fan of HxH, I've enjoyed it.