So, I've been playing for a long and good while from now (around when ECA was first released on 1.8) and, with the gameplay of other peeps in Youtube, I wondered myself on the most difficult factions most ROTR players face off against. So, speak up down in this topic, and share how you guys deal with them.

For me, being a ECA main, it's Russia. Now, I could go on a very long rant about how they made this faction (least on the current beta test) TOO OVERLOADED that it's not even fun playing against a hard or medium AI on a map with big/no chokepoints, but maybe it's just the AI or (I can admit this) me still in on the novice-apprentice levels on RTS principles and strategies. Plus, personally, there are more important stuff to do other than rant about that godsforsaken faction. Other factions, I can do well against (US? Just build tons of AA, guard it with a few anti-ground defenses, some sensor arrays and a few Grand Mortars can do the trick. China? Tons of Guard Towers, Gun Turrets, and mortars, with the support of Wotans and ECAn aircraft. GLA? I eat that for breakfast due to their lack of armor) but Russia is the faction I'm finding myself saying "I can't do anything against this" when they go full unrelenting mode, even with the late game prototypes (Venom being my personal and absolute favorite). How I deal with them? Wait and hold until late game, have Frank Jaeger sneak into their base and nab some free cash while holding out, then get the Protocols, build me army, have Jaeger disable their power, combine the devastating power of two Solar Bursts, a Grand Slam bomb and a Smart/Neutron bomb then start the assault on their base. If something compromises said plan mid-way, retreat the most important units back, rebuild/improve army, and rinse and repeat. Works like a charm on choke maps.

Feel free to also rant about the said faction below, but keep it as minimum as you can.
All opinions are respected. Have a good day, fellow Kommandants!

Depending how the AI is coded, I think USA is the hardest to face.

Lots of support + pesky nighthawk + Tomahawk (Cruise missile) can be a pain in the @55 when faced all of them together.
Don't forget the Burton sneaking up your base and blow away you powerplant.

Not a rant but people are aware that even in PVP russias really easymode

To me it depends what aspect you are talking about.
- If trouble comes from resisting enemy attacks, then yes, I agree with you, Russia is the toughest. A thing that helps, as ECA, it the massive use of penetrator rounds. I know the tooltip says it deals less damage, but you can use them very effectively against super heavy tanks. It helps a lot. Also, using Jagdmammuts is a great way to reduce their numbers. As for infantry, any mortar can be loaded with canister rounds, which are deadly.

- If trouble comes from actually defeating the enemy, then I would say that ECA is the hardest. For one, Artillery is absolutely mandatory, since Gun Turrets and Guard towers mow down all your troops with ease. But even with that in mind, you have to deal with Mortar Pits, that you don't always see at first glance, and often fire from out of your sight radius. Grand Mortars are less problematic, due to less range, but also deal a lot of damage. Troublesome, but not horrible. And as if it was not bad enough, Tigers are in almost any ECA build, so AA is also something to invest in. Their offensive potential is lower than other factions, but they are really a tough nut to crack.

- USA is a special case IMO. Mizo did program the AI by giving each faction 3 "personalities", that match more or less the 3 generals for 2.0. And USA has the most diverse generals (infantry, tanks and aircraft). So when you face USA, you can really be in trouble if they have a persona you're not prepared against.

- GLA is quite easy, bar the massive hijacker spams.

- China is not complicated either, but you can be quickly overrun if you're not careful with your production. And also they tend to mine every single building, so they are very good defensively speaking.

The problem with russia is that its too good at combined arms warfare. With msta/hellion/bombardier and powerful tanks like golem/sentinel.
Note I dont know why this is case though, russia's main thrust is tank warfare, not helicopter/artillery support.