Honkai Impact 3rd vs RWBY

Connection: 

Both are white and blue themed prodigal fighters hailing from powerful families (Schariac/Kaslana household and Schnee family respectively)

Both are the older sisters to the series' white-haired heroines (Kiana Kaslana and Weiss Schnee respectively)

Both are part of a military organization (Schicksal and Atlas respectively) that assign superhuman defenders (Valkyries and Huntsmen/Huntresses respectively) to fight against the monsters seeking to destroy humanity (Honkai and Grimm respectively)

At one point they were temporarily villains as they were ordered to fight their younger sisters from their superiors (Otto Apocalypse and James Ironwood respectively) but they defied and rebelled against them

Both also acquired a new power which helps them in defeating their former superiors (Durandal obtains Palatinus Equinox and kills Otto with Herrscher of Flamescion Kiana. Winter becomes the Winter Maiden and beats Ironwood)