Second picture of it. Looks almost identical upside down.

That's pretty dumb... after posting the second pic, the one on my first post disappeared!

I'd like to see the other picture. But this looks to be the larvae of one of the Tortoise Beetles. Tortoise beetles love plants in the Brassicaceae family.....such as your radishes.

I reposted the first image. Thanks for the reply!

Wait until you see what the adults look like! It's one of the most appealing looking beetles but are considered a minor pest of cruciferous vegetables.