What if,We hard brick our phone? topic

Hello,we all know that if we root or flash a custom recovery knox counter will be triggered & we'll loose our warranty.Now if the device faces some kind of hardware problem,can we hard brick our phone by flashing some wrong kernel & saying samsung that it's dead by its own?Also if download mode is available after hardbrick?
Sorry For the silly question
Im running a non rooted stock rom

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