I assumed a behavior of strictly Muerte al inocente and using nothing else, even when rooted by Guttergunk's Barrizal. The strategy worked fine, took me 64 seconds in 11 rounds.

Script:

use(Murder the Innocent:2223)
change(next)
standby

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It went even faster on second attempt when I had Baa'lial use its other abilities while waiting for the root effect to fade. For this attempt, after using Murder the Innocent, I had Baa'lial use Manifiesto del odio and followed up with Pisotear. Then I switched to Buscamuerte and used its Murder the Innocent to finish off Guttergunk. This took 48 seconds with 7 rounds.

I did a third attempt to confirm the results of the previous one, but for whatever reason Baa'lial died before I could use its Trample. So instead I immediately swapped in Death Seeker, used its Murder the Innocent, and then used Robo de alma twice to defeat Guttergunk. It still took 7 rounds at roughly the same amount of time.

Script for modified strategy:

use(Murder the Innocent:2223)
change(next) [round=2]
use(Hatred Manifest:2505) [round=4]
use(#1)
change(next) (editado)