South Carolina didn't “try” to secede - they did secede. Later, when it was determined it was in the union's best interest to acknowledge the fact, the federal government required South Carolina and other former states to be readmitted to the union.
Lincoln, of course, pretended they couldn't secede and that was the official basis for Lincoln's War and all the killings. Six hundred thousand by some accounts.
southern slavers unhinged because they lost an election, pretended to secede and within weeks took to armed insurrection to force their way out of their union commitments. That was the official basis for the Slaver’s War and all the killings. Six hundred thousand by some accounts.