This is a simple but beautiful Druid combo that could result in a fantastic, memorable, very short fight.
The spells: Wrath of Nature and Druid’s Grove (from Xanathar’s Guide to Everything). Just keep in mind that the latter has a 10 minute casting time (long, but not terrible considering you’re going to have to plan ahead anyway) and a very, VERY specific material component that must be supplied.
This one takes some setting up. You’ll need to (1.) know that a fight is coming up and (2.) have some ability to influence both where and when it happens. This is a daunting obstacle, but the planning itself could be very enjoyable. Have the party rogue or diviner do some spying on a significant enemy for the party – maybe a recurring baddie or a fearsome creature they’ve been contracted to hunt. You could wait for sometime when they will already be in a particular wooded area or take action to lure them there yourself. The possibilities are endless.
Once you get them there through whatever means, choose an area 60 feet on a side within this woodland where you plan to set your trap, and cast the two spells. At 5th and 6th level, the cost is high, but the reward so much more so. Welcome to your new death trap. In this area now:
-The area is difficult terrain ONLY for your enemies
-Heavily obscuring fog subsists that ONLY affects your enemies. It also slows them severely, so every 5 feet of movement now costs 20 feet for them.
-A 20 foot radius of spikes appear, doing 2d4 piercing per 5 feet moved, ONLY to your enemies.
-You awaken 4 trees and give them movement, each of which obey your commands and deal 3d6+4 damage on a hit.
-At the beginning of your turn, each enemy within 10 feet of a tree must make a dex save or take 4d6 slashing damage (including the awakened ones that you can move into position every turn).
-At the end of your turn, one enemy must make a strength save or become restrained.
-As a bonus action, you can fling a rock loose for 3d8 bludgeoning damage.
If you go the extra mile, you can have another caster help out by closing off any means of escape with a wall of stone, thorns, force, or fire, forcing your foes to endure your now blender-like, verdant hellscape.
Lastly, wild shape into some sort of terrifying predator – maybe a dire wolf, deinonychus, or even T-Rex (if you’re in the Circle of the Moon) – and stalk your enemies through the stone-flinging, tree-whipping, grasping, spine-covered fog, using the awakened trees to herd your prey toward your waiting jaws.