Leupold and Vortex are probably the top two scope company warranties, with Sightron being up there also. I've used Sightron's warranty twice over the years after breaking a SII and a SIII series scope. Their CS was top notch, and they replaced / repaired the scopes no question's asked.
Swarovski also has great CS and warranty service, I had an older 4-16x50 Pro Hunter that I'd used on several hunting rifle's over the years and it quit holding zero. Swarovski completely rebuilt the scope and included a bunch of swag when they returned it.

There are plenty of optics companies that have let customer's down when it comes to "Lifetime" warranties, mainly Nikon, and the Weaver & Bushnell brands now owned buy Vista Outdoor. Steiner scopes warranty service has problems also since the Beretta Group owns them.