Steins;Gate
Both use time loops as emotional torture machines rather than easy fixes. Steins;Gate is sci-fi and Re:Zero is fantasy, but fans who liked watching a protagonist break down under repeated consequences usually connect with both.
Erased
Erased is another common time-reset recommendation because the protagonist must use repeated chances to prevent tragedy. It is shorter and more mystery-focused, but the urgency of changing one fatal timeline matches Re:Zero's core appeal.
Mushoku Tensei
Both are isekai series that take character growth, trauma, and emotional consequences more seriously than a simple power fantasy. Mushoku Tensei does not have Subaru's loop mechanic, but it shares the focus on flawed people trying to become better in a fantasy world.
KonoSuba
KonoSuba is usually recommended for the opposite side of Re:Zero: the isekai parody, useless party dynamics, and fantasy-world comedy. It is much lighter, but fans who enjoy Subaru's messy interactions with a dysfunctional cast often like the comedic version here.
Higurashi: When They Cry
Both involve repeating tragedies, hidden rules, and the horror of realizing that a timeline is going wrong again. Higurashi is more mystery-horror, but the loop-based dread and gradual reveal structure explain the frequent recommendation.