As Sin enters, remove all counters from any number of artifacts, creatures, and enchantments. Sin enters with X +1/+1 counters on it, where X is twice the number of counters removed this way.
When Sin dies, put its counters on target creature you control, then shuffle this card into its owner's library.
Sin is a Simic +1/+1 counters payoff that turns your whole board's counters into a massive flying, trampling threat. Spend the early game building counters on cheap creatures with proliferate and counter generators, then cast Sin to vacuum them up at double value for a one- or two-swing kill. Its death trigger reroutes the counters onto another creature and shuffles Sin back in, so it's hard to permanently answer.
Built-in resilience: dies trigger preserves your counters and recurs Sin from the library
Doubles counters on entry, creating an oversized evasive threat very quickly
Flying + trample makes it a reliable commander-damage and finisher creature
Synergizes with the entire proliferate/counters package that Simic does best
Rewards going wide on counters across artifacts, creatures, and enchantments
Seven mana is slow and the payoff is weak if you have few counters to remove
Removing counters can shrink your other creatures or wipe useful keyword/loyalty counters you wanted to keep
Vulnerable to exile, bounce, and -X/-X effects that ignore the death shuffle
No interaction or card advantage built into the commander itself
Telegraphs lethal damage, inviting blockers and removal before you connect
Legendary Creature — Leviathan Avatar
