Vexilus Praetor

Targeted removal, tuck effects, Commander-damage math, aura-based lockdowns, deathtouch pingers: a huge slice of the toolkit built to kill a general depends on interacting with that creature directly, and this body opts your commanders out of every piece of it at once. Protection from everything is the widest single-target protective grant in the game (can't-be-targeted, can't-be-blocked, can't-be-enchanted, prevents all damage from every source), and extending it to a whole class of your permanents is a scope no individual protection spell reaches. The card is not defending itself; it's a warden posted over your most important creature, which changes how it must be answered. An opponent who wants your general dead now has to remove the 3/4 first, and the flash lets you seat that guard on their turn, in response to the spell that was going to resolve on the commander. Vigilance means the warden never has to choose between holding the line and applying pressure. The umbrella has honest gaps: it does nothing against untargeted sweepers like Wrath of God, and edicts that make you sacrifice sidestep it entirely by never touching the protected creature. Its own protection is conspicuously absent from the grant, so the shield does not shield the shield-bearer. Kill the Praetor and the whole umbrella folds, which reduces the exchange to a single question: can an opponent profitably spend removal on a four-mana creature to unlock the removal they actually wanted to cast.