Tandem units that give you problems...

Snipers behind Missile Squads.

Nothing worse than Cyborgs backed up by a Basilik or two for me. Man I hate it. Only way to stand a chance is an Ion Cannon at that point. Lol

For me flame troopers and attack bikes... also air units, lots of air units from banshee to venom to orca and talons. Tech is no issue for me as I usually go after their harvesters to borrow some of their money to fuel my economy. Some combos like disruptor and zone trooper is still a bit worrying.

My Biggest Issue is Juggernaut behind Zone Troopers.

I enjoy playing my General Solomon Deck.

My General Solomon Deck doesn’t have an Air - Vechical Counter.

The Juggernaut ends up 1 hitting any unit I bring out towards it.

I would need to get super lucky to take it down.

Otherwise, I auto lose.

A few other combos you can add to your list which I have enjoyed using against people include:

-Giga Cannon behind Fanatics 

-Giga Cannon behind Cyberwheels 

-M.L.R.S behind Wardogs 

Basilisks and Kodiaks... I dread those when they come out because my deck is not suited against these flying battleships. I need to train 2 laser/missile squads just to eliminate one. I feel safer as Nod when they aim at my tick tanks. At least they can delay the pad from being stolen, allowing me ample time to send my cheapest anti-air. If the deck was 7 cards, my phantom/hammerhead would join and the Basilisk/Kodiak issue would resolve. I don't know if I should remove the buggy/rhino or the cyber-wheels/war dogs. The wheels/dogs are my scouting unit and helps me against scarabs and MG nests by spotting them early before my opponent has the chance of attacking. The buggy/rhino is useful against some infantry units and most importantly early air units like venom, talon and drone swarm. The laser/missile squads deal with Orca, banshee and laser drones.