Alot of the shippers will use two bags, oxygen, heater packs, and bag buddies to keep the fish calmer. Some sellers will even fast the fish for 2-3 days so they don't make as much waste. If you are against sedating fish, then ask the seller first.
I ordered Some WC Moba Frontosa and we had bad weather. The fish were delayed an entire day, they spent 2 full days in a bag and have been doing fine in my tank for the last 6 months. I thought I was gonna open the box and have 3 dead 6-7" Mobas.
I have ordered corals, inverts, and fish from different sellers; I have yet to receive a delivery with a dead fish in it.
One last thing, check the return policy. Many places want a picture of the dead fish in the unopened original shipping package. They may also only offer in store credit.