I ordered 2tb of seagate HDD for my upcoming build, but I've heard that seagate Isn't reliable? Will it work fine? I got it on a sale so that is why I pulled the trigger on it.
It's just as reliable as any other mainstream hard drive.
The things about Seagate being unreliable are from a study that was debunked because of poor methodology. People still like to quote it as though it's gospel truth, however.
You'll be fine, congrats on nabbing the sale!
Seagate had some pretty bad 2T drives [one specific model] about 5 years ago (or more), I don't think anybody (including Seagate) has had anything similar that sticks in peoples minds. Right now, all consumer drives are pretty good and there isn't really a good reason to avoid one.
While people like to disparage the backblaze data, if you want to measure hard drive life expectancy in an "accelerated testing methodology" (i.e. finish the test before the HDD is obsolete), Backblaze's use case is pretty much the textbook example of how to do it. It might not be very good data, but it is still the best you can find. And for years Seagates have been pretty similar to everybody else.
Hard drives, particularly consumer grade, are basically a commodity now. If your Seagate makes it through the first couple months, and it probably will, it's likely to last longer than you want to use it.