What kind of laundry detergent should I use for childrens consignment clothing?

I buy some of my son's clothing at children's resale shops. I bring them, wash, dry & iron the clothing just to give me the peace of mind that its clean & stain free. But you just never know with what the clothing fibers have. My question is: what kind of laundry detergent is best to wash clothing like this? What steps would you take to guarantee cleaniness of this clothing?

Thank you for your answers.

I use cheer or tide that has bleach in it. Use the hottest water the fabric will allow.

Just get one of the better ones like the oxyaction ones. They use oxygen to remove even more such as traces of blood. You could use a basic laundry detergent, plus a scoop of a stain remover for colours, and then if you spot any specific stains use a stain spray on them.