In this RPG, you don't have to kill anyone. Each enemy can be "defeated" nonviolently. Dance with a slime. Pet a dog. Whisper your favourite secret to a knight. Or, ignore this choice and rain destruction upon your foes.
The best chance at playing Undertale at recommended sys specs on a 1920x1080 screen resolution will be if your PC has at least the GeForce 210/Mobility Radeon HD 5450 graphics card. The CPU required to meet recommended requirements is either an AMD Sempron 3000+ or Intel Celeron 2.0GHz processor. This type of gaming rig will deliver you around the 60 Frames per second. System memory required for Undertale is 3 GB performance memory. Taking a look at the min reqs you will require a Radeon X1650 GT graphics card with a Celeron 1.66GHz or Sempron 2200+ processor to reach the minimum Undertale specs, run on low graphics setting and 720p. Another thing to consider is the DirectX capability of your GPU. Undertale needs a GPU capable of running DirectX 9. Recommended needs around a 10 year old PC to run.