In the anime adaptation of Re;zero s2 parts 1 and 2, created by Studio White Fox, there are many issues that are done subpar in the anime and exceedingly better in the light novel, elements that are missing out with different levels of importance and impact, some of which would be easily fixed. Reading the light novel is hard and cannot be expected from anyone, yet some mind-blowingly good aspects are not included and even entire characters are given injustice.

There are others, like the Elsa being crucified changed to encasement in purple matter/change of state to this matter, which regeneration doesn't explain escaping from while it did crucifixion... but the main ones are these:

1. The fact Garfield is done injustice by removing 30% of his epic aggression together with all his swearing, which at least in the English translation make the character stand out uniquely and makes him twice more fun than in the anime. To give an example of these lines this is what he says after Subaru tells him Emilia told him she loved him. Garfield: So fuckin' what!? It was already obvious when y'got here that Half-Witch's fuckin' glued to ya. If y'wanted congratulations for y'two gettin together, rippin y'two to shreds would fuckin' do it—"
-Perfection.

Second is the lack of the element of forced mind control to have feelings for Satella when Subaru meets her in the witch's tea party along with resurfacing MEMORIES of him having loved her, and her words to hint of having shared time together despite us never seeing it. This was mind-blowingly creepy and epic and had magnificent ramifications for theory-crafting the plot.

Third is the way they handled Roswaals bet. They should've had the scene in, where Roswaal makes Subaru form a contract that binds his soul forever, even after he dies, to abandoning HIS HUMANITY for good would he lose the bet. Major stakes. Without this element, although mentioned at part at the very end in the anime, the whole bet becomes ridiculous and unbelievable, childish even, breaking all immersion, as there's no incentive for either party to follow "the bet" through.