I will be roadtripping to Tampa for the Outback bowl game leaving on Sunday. Planning to stay in Atlanta on Sunday night (12/28). Anyone have any suggestions on Atlanta nightlife on a Sunday?

Atlanta nightlife on a Sunday evening? You might try praying. More seriously, you may have hit a seasonal dead spot. Not too much in town. Might look at accessatlanta.com. You don't identify your interests, so more specificity is difficult.
If by "nightlife" you mean clubs and bars, try toney (to fledgling dilettantes) Buckhead (north of downtown)--bullet-proof vest optional but recommended, or Virginia-Highland (east of downtown), wall to wall higher-end drinking establishments often teeming with people seeking to team.

What about Sunday night football? Any sports bars to catch the game with any kind of crowd or excitement?

Not my turf. Accessatlanta.com has a subcategory under "restaurants" for "sports bars." The list appears to be a compilation of paid advertisers. Might also try Dave & Buster's or Jock's & Jill's (I recall the latter is-or was-owned by some pro athletes), depending on where you'll be staying and how far you wish to stray. Atlanta is big, and, it has a large number of watering holes with large screen televisions, some in Buckhead (including ESPNzone) and Virginia-Highland. I strongly suggest you avoid downtown and south Atlanta.

I was gonna say, I think Jocks & Jills may be what you are looking for...I lived nearby and it was always buzzing...Have Fun !

I'd agree with hmmm and recommend ESPNzone in Buckhead, but it's true that a bullet proof vest is a good idea.

That ESPN Zone in Buckhead is always busy.

What has happened to Buckhead?