While 2's are the highest value cards, they can be beaten by Bombs. Once a Bomb is played, it can only be trumped by another Bomb. Bombs are formed based on unlockable Athlete Abilities according to these six classes:

4 Rank Combo
Card Combination: four cards of the same rank
4 Rank Combo example: four 5's, or three Jacks + a Wild Card

Aces Wild Kick
Card Combination: one Wild Card + one Ace (any suit)
Aces Wild Kick example: a Wild Card + Ace of spades

Double Slam
Card Combination: A pair of Aces (any suit) + a pair of any other rank and suit
Double Slam example: a pair of Aces + a pair of 7's

Straight Flush Bomb
Card Combination: Five consecutive cards of the same suit
Straight Flush Bomb example: 5, 6, 7, 8, 9, and 10 (all hearts)

4-4-2 Counter
Card Combination: Card 2 (any suit) + a pair of 4's (any suit)
4-4-2 Counter example: a pair of 4's + a 2 of diamonds
Royal Trips
Card Combination: Three Queen's (QQQ) or three King's (KKK), any suits
Royal Trips example: three Queen's or two King's + a Wild Card