Make the vanilla pudding layer: Whisk the cold milk and vanilla pudding packets in a large mixing bowl until it starts to thicken, about 2 minutes. Then, blend in the sweetened condensed milk.
Make the whipped topping: Using a hand mixer, beat the heavy whipping cream on high in a medium mixing bowl until stiff peaks form. Fold 2/3 of the whipped topping into the vanilla pudding until well incorporated. Then, mix the powdered sugar into the rest of the whipped topping. Store both these dishes in the refrigerator until they are needed.
Slice the bananas into 1/4-1/2" pieces. Start with 1-2 bananas. Slicing the bananas as you go will ensure they don't brown while sitting to be assembled into the dessert.
The assembling: Next, reserve a handful of vanilla Wafers(about 1/5) for the garnish. Then, slightly crush a remaining 1/4 of the wafers on the bottom of the trifle bowl.
Then layer 1-1 1/2 sliced bananas onto the crushed wafers.
Dollop 1/4 of the vanilla pudding on top of the vanilla wafers and sliced bananas, and carefully spread the pudding into an even layer. Repeat this process 3 more times for a total of 4 layers. Then, chill the banana pudding dish in the refrigerator for 2 hours, allowing the layers to set and blend.
Garnish and Serve: Take out the remaining whipped topping, your reserve of vanilla wafers, and the last banana. Add one more layer of vanilla wafers(don't crush these; reserve 4-5 wafers for later) and sliced bananas, and top the dish with the whipped topping. Garnish with a sprinkle of any remaining crushed vanilla wafers on top. Serve chilled and enjoy!