So I started work as a software developer during college, and the people there were really nice to me and endured my constant absence from work because of college stuff.
Now that I graduated, I got an offer as a software engineer for 1.5 times the salary I currently have.
Should I take this job and forget what the people at my current work did for me?

I would take the details of the offer to your Manager/HR and ask them if they can match it. If they were so willing to help you with uni, they'll more than likely match the other company's offer as well

Money isn't everything man, I'd rather work with awesome people for free than get paid to be quiet/shitty workplace (unless you need to pay the bills), but it's your choice anyway

Let them know, see how much they can match it.
1.5x is a big difference to you, but to them it might not be that bad. If you haven't gotten one after being there for a while, you deserve a raise : if they were willing to pay x for your partial attention, your full attention should be worth a bit more.

They have been good to you, but remember that business is business. Let them understand you, give them proper time so that you don't disrupt their business. No one will blame you for going forward with your life, as long as you don't do it in a sickish fashion.

On the other side, if you feel indebted to them and want to repay them, this is also an option, but only do so if you already feel comfortable with your income and context.

ask your current company to give you the same salary. If they can't, do some research about the company that offered you a job. If they are good, say goodbye to previous company and embrace the new one. If they have been kind towards you, they will understand.