For the meta of Coolboy and many tamers in use, the Dexmon sometimes appears in the battle for free. This is a game-changer for Security Control when not many OTK deck have option cards to destroy Dexmon (except for the Security Control deck itself). Dexmon "On Play" triggers "De-digivolve 1" to all opponent's Digimon and delete all of opponent's LV4 or lower Digimon. On top of that, at the end of opponent's turn, delete all of opponent's Digimon with lowest play cost. This effect makes the opponent always has to throw out a lv3 or a lv4 Digimon that is available in their hand to avoid deleting their big boss in the battle. We normally see 3 or 4 copies of Dexmon included in BT9 security control deck.
Option Cards
There are many new option cards that are available to use for Sec Con. To defend, now it is not about Gaia Force or Atomic Blaster anymore because these are not effective against many meta decks. These days we see more cards that their effects would return the opponent's Digimon to hand/deck or security stack like Chaos Degrade, Cocytus Breath, Ground Fang or Flame Hellscythe.
Glad that Yellow is still a strong contender in this OTK meta. People be hating on Yellow because it can recover and is loaded with Options but at the same time they're playing an OTK deck with an immune boss Digimon that checks 2~3 securities per attack, restands, and is mostly safe from checking security either through immunity or very high DP like Alphamon Ouryuuken / Grandis. It gives balance to a somewhat highroll meta.
Yes, Currently we have Security Control and Armor Rush MagnamonX can counter the BT9 OTK meta.