Think about what you want really. What's a violent explosion in real life? Lots of shrapnel, smoke and a big fireball, what else? A shockwave? Maybe some shaking camera action or a blinding bright light to top it off?

Then take those things and see how many you can do in TPT and how. What's a shockwave? It's a wave of high pressure. You can totally do that in TPT. What else? A fireball? Pfft. That's easy peasy. Shrapnel? You could pull it off...

After all that, put those accomplishable things into an element of your very own design.
There are functions in Lua to change pressure in a given square, there are functions to create elements and destroy them, you can use various properties to create fire too.

Welcome to the world of invention.