Nice of you to join us four generations after Eelektross was introduced, with an observation that is not actually entirely accurate.
Yes, Eelektross is certainly an Electric-type with Levitate, which provides some innate protection against its biggest weakness – but that does not mean you can't actually land a super-effective hit on Eelektross at all. Levitate is an ability, and there's all sorts of ways to get around that.
In fact, even in Gen 5, when it was first introduced, there was a fairly easy way to counter its levitation – take a Pokémon with the Mold Breaker ability, such as Haxorus, give it Earthquake... and suddenly the delightful murder windsock isn't so protected from seismological-based death. There are plenty of more niche options for knocking a flying/levitating Pokémon down to the ground, or for neutralizing/changing a Pokémon's ability or type to peel off that layer of protection - which means that Eelektross, while it
is godsdamned awesome, sure as hells ain't invincible.
And while I'm sure the discovery was pretty exciting for you – welcome to
Today's Lucky 10,000, I guess! – it also has practically no discussion value, so I'm going to lock this thread now.