Looking for extremely brutal movies similar to Frontier(s), Martyrs, Inside, High Tension, and Hostel

I'm looking for brutal movies that are a bit more grounded than something like Terrifier.

Movies I've seen that are similar to what I'm looking for:

Frontier(s)

Red, White, & Blue (2010)

Martyrs (2008)

Hostel 1 & 2

Inside

Saw

High Tension.

Movies that aren't what I'm looking for:

Terrifier (too outlandish)

Serbian Film (Too outlandish)

Thanks, guys.