Trifarian Shieldbreaker Rework
Currently, the card is competitively unplayable. It has really cool artwork and design; it is a shame that the card does almost nothing in any game mode, regardless of competitive play being abandoned.
For the rework, I looked at the Flavor text of the card, which is "I don't have the patience for a siege. Send the Shieldbreakers."- Darius. Meaning this unit thematically excels at punching through the fortified enemy defences.
What each Keyword represents:
Fearsome represents the intimidating figure and warriors fleeing in the artwork. Also, the voice lines "Run while you can!" and "The craven will fall!"
Overwhelm represents that you can't stall; put chaff blockers in front of it. Its main job breakthrough the defences of the enemy.
Passive 1 represents that this card is specialised at breaking through fortified enemy lines. Its job is to deal Nexus damage and end the siege no matter what. Granting +2 permanent power can also refer to the voice line of "We are forged in war."
Passive 2 represents the Vanguard aspect of the card, which can be seen in the voice line "Vanguard!". This is the Vanguard Shock Infantry force, meaning that when they disrupt the enemy's defence and formation, the rest of the Noxus army will have the upper hand. It automatically rewards the card attacking first, which directly represents Vanguard.
Allegiance is mainly for balance reasons, but it can be interpreted as the fanatic loyalty of the card, as in the voice line "As Noxus wills!". Or as a very elite unit that is almost always only used by elite Noxus armies, and it is naturally compatible with them.
My only concern is that the card might be a bit too strong, but I am not sure. Since Overwhelm is a very strong and effective keyword, it might be on the stronger side.
But since the opponent will decide the blocker, the first passive depends on how the opponent will react. The card is not a good blocker. The only time it would be kind of a lose-lose situation for the opponent is if allegiance was triggered and there were already multiple Noxus units present on the board.