Here is a list of gods with knock-ups (alphabetical). If you do not have the God Pack, just wait for one of the below gods to pop up in the free rotation and try for it then
Gods with Knock-up AbilitiesAnhur - "Disperse" (third ability) - If you pounce on an enemy they will be knocked up.
Awilix - "Moonlight Charge" (third ability) - This one is a bit tricky to hit. If you hit an enemy from the side or from behind, they will be knocked up.
Bacchus - "Belly Flop" (third ability) - When you belly flop onto enemies they will be knocked up.
Geb - "Shockwave" (second ability) - When you use this, all enemies in the cone radius will be knocked up. Probably the easiest to get this with.
He Bo - "Water Spout" (third ability) - Enemies hit by Water Spout will be knocked up.
Hercules - "Earthbreaker" (second ability) - Enemies hit by the very edge (furthest away from you) will be knocked up.
Jing Wei- "Persistent Gust" (first ability) - Enemies who walk into the circular radius will be knocked up.
Kukulkan - "Spirit of the Nine Winds (4th ability/ultimate ability" - Enemies in the linear path of your ultimate will be knocked up.
Poseidon - "Release the Kraken" (4th ability/ultimate ability) - Only enemies in the very center of the Kraken radius will be knocked up. I got this achievement using Poseidon.
Sobek - "Tail Whip" (second ability) - Enemies in the circular hitbox of this ability will be knocked up.
Sun Wukong - "72 Transformations" (third ability) - Transform into the boar by holding your crosshairs close to you (medium range is tiger, long range is eagle). The boar will knock up enemies you collide with.
Sylvanus - "Wrath of Terra" (4th ability/ultimate ability) Enemies in the area of effect will be knocked up.
Tyr - "Fearless" (first ability) - You can only use this in your assault (red) stance. You will move in a straight line, and knock up any enemies you come into contact with.
Vamana - "Clear the Path" (first ability) - When you activate this ability you will start dashing around. Any enemies you bump into will be knocked up.
Xiang Tian - "Hook Slam" (second ability) - Any enemies in the small cone radius will be knocked up.
The game classifies some of these as "knock backs" as opposed to "knock-ups", such as Kukulkan's ultimate, but I have tested in a lobby and can confirm they count toward the achievement.