I'll start - I don't shop a lot, but if I had to buy stuff like hardware parts, I do use Amazon sometimes, but if I can, then I try to use Flipkart. Realizing how it has turned into a monopoly, I try to look for alternative websites, and check if they're trustworthy.
If I remember correctly, the last three items I've bought online were hardware parts from some local websites. The chi-fi IEMs were bought through headphonezone.in, and they were super-fast in delivery - I had to wait for only four days.
Not sure what "a lot" means but there's some animal veterinary stuff that we buy every 6 weeks or so because... well... shit's expensive and not always easy to find locally. It winds up being either Amazon or Chewie that has the stuff in stock and at prices (even with shipping) that are manageable with our budget.
amazon sent my friend a bottle of animal medicine, which was clearly already opened, with the liquid clearly refilled with a mystery fluid, and filled all the way to the cap.
Most of the stuff is in sealed and tamper evident containers, so at the very least, we'd know something was up before trying to use anything.