The term 'omega' is an archaic, outdated term that is no longer used in modern scientific discussions of wolf pack hierarchy. There are no 'omegas' in true wild wolf packs, which consist of the breeding pair, the siblings of the breeding pair, and the breeding pair's pups. 'Alphas' and 'omegas' only exist in captive zoo packs, in which unrelated wolves are forced together and make an 'alpha/omega' hierarchy just to keep themselves from killing each other.
And Milkfur, remember that lions live in prides. Lions (and big cats in general) have superior stength and agility, as well as a higher bite force and retractable claws. A pack of wolves may be able to drive away a lone cougar simply because they strength in numbers, but an entire lion pride versus even a large pack of wolves is very likely to emerge victorious because they have better weapons as well as strength in numbers. It's like a group of people with swords versus another group of people with machine guns.
Felines are typically lone hunters who are built to ambush and quickly overpower prey, which is why they need those superior weapons just to survive from day to day. Canines are typically pack hunters who are built to run over long distances and slowly wear down their prey, so they don't need to have retractable claws and super-strength. This doesn't mean wolves are not strong. It just means they're not as strong as felines.