What combination of alcohol and pills is fatal?

[Braindead Atheist]

I need something I can just pick up at the store. I want to do this before the year is over.

 

[unkuto]

I dont know it would work like that. Most stories about drinking pills + alcohol either from movies and myth itself come from 50-60s when they used N in sleeping pills and people would just easily overdose. I highly doubt you can kill yourself with anything that can you easily buy at the store.
Humans are really hard to kill. You'll just throw everything out or sleep really really long time and wake up with a headache,

 

[Avalanche81]

You would have to yet your hands on some potent prescription to even have a chance. OTC drugs are made now not to be able to OD.

Unkuto is correct you'll wake up with a massive headache or puking all night.

I was able to get my hands on some prescription drugs and if I wasn't found by a family member I would've succeeded.

Let me tell you being in the ICU for a week was worse then pills and alcohol. I'd rethink your plan or give yourself some time to rethink the whole idea. You did give yourself till the end of the year so you have time to rethink all of this.