Best ways to kill a Tier 1 caster without being one

[crizh]

Give him no reason to know you intend to make him dead, then at random cast Silenced Quickened True Strike and Silenced Disintegrate from behind. At his spellbook.

(Note: This can only be expected to work on actual wizards as played in-game, not the hyper-paranoid hypothetical superwizards that have contingency plans for everything that like to loiter around this forum...)

What is that, a level 15 caster?

How are you squeezing Ranged Sunder into that build?

AFAIK, RAW, you flat out cannot target an attended object with a Ray.