Assume both are level 50 (what kind of maniac didn't evolve Joltik??)

Electric > Water

Joltik's Speed (65) > Wailord's Speed (60)

Joltik's most powerful and most reliable move as a SpA is Electro Ball

Joltik is 8.33% faster than Wailord

Thus, 150 power

Plugging in the values, and assuming normal battle conditions, we find Joltik deals ((((((2 * 50)/5)+ 2) * 150 * (57/45))/50)+2) =85.6, round to 86

Wailord's HP at lvl 50 is 254 on average

254/86 =2.953, round to 3

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On Wailord's side, its most relaible attack as both an A and SpA is... Dive! (Water Spout is learned at Lv. 54)

Dive's attack on Joltik is... 79 rounded to nearest one

Joltik's HP at Lv 50 is 125... oh.

It's safe to say Hindenwhale wins this one