A pokemon that forever impresses me (In both Reborn and Rejuv) is physically bulky Dedenee. I'm about vouch so hard for my boi here.
First of all, it's learnset is superb.
Having access to either Nuzzle or Thunder Wave (nuzzle is taunt proof, but thunder wave doesn't make contact and it's easier to use when catching wild pokemon.) Charm is essential to curbing physical threats and navigating boss battles without using an intimidate mon.
Dedenee's strongest tool is Parabolic Charge which hits all adjacent pokemon on the field healing for 50% of the damage done. This move is disgusting in double battles when utilized to its fullest potential- letting you bait out the AI into thinking that it can take down Dedenee before healing.
Finally, Dedenee naturally learns Volt Switch which further supports your team overall. All of these moves are obtained by level 30.
Dedenee's rare typing lends it to being a great tank too:
Resists: Electric, Fighting, Flying, Bug, Dark
Weaknesses: Poison, Ground
Immunities: Dragon
To top that off it has access to two strong abilities being Pickup and Cheek Pouch.
Considering the late game I have not tested out...
...to see what Dedenee's additional options are with those.
Here's a pickup Dedenee with minorly scuffed EV training that I'm rocking with. I have just defeated the fourth gym leader and its spot on my team is irreplaceable so far. While stat-wise Dedenee will fall off later into the game,- I think that Dedenee still has a lot of unexplored potential.