Both asyndeton and polysyndeton give equal weight to each item in the series and often emphasize the items in the series. Polysyndeton also emphasizes that there are a lot of items in the series.
Asyndeton is when no conjunctions are used in a series.
The witch—wicked, heartless, conniving—shows no sympathy towards the two children who begin eating her house.
Disappointed, disheartened, defeated, the team walked slowly back to the bus.
Polysyndeton is when multiple conjunctions are used in a series.
Before I could take a break, I needed to finish my homework and walk my dog and make dinner and water the garden and call my grandmother and clean the kitchen.