There are a variety of areas that your mecha needs to address. You might can overlook some of these, but the more you cover, the better your mecha will fair against tanks...
Balance and Computing Power
You need faster computers. The current state of the art for balancing robots isn't sufficient to meet the demands of combat and moving at speed. These demands are going to require computers that can react to sensor readings to provide necessary responses to shifting balance in real-time.
Sensors and data
You need more sensors that can send data more accurately and faster than today's systems. Your robot must have massive amounts of data about the 3D layout of the terrain, the robot's own body positioning, ground material (hard surfaces require different balancing techniques from soft; wet surfaces balances differently from dry; slick surfaces react differently than high-friction...), weather, and oh, yeah, what the enemy and ally forces are doing... And all of that data has to be perfectly reliable, 100% of the time. If you have one sensor array for everything, and a sniper hits it, your robot is done. So that means redundancies.
You have to minimize weight. Armor is heavy. Engines are heavy. Fuel is heavy. Munitions are heavy. You need to reduce your weight as much as possible for a variety of reasons. Lower weight means more mobility: higher speeds, faster changes of direction, and fewer restrictions on passable terrain (try taking a 70 ton main battle tank through a shallow lake). Lower weight means you have a system that is less likely to be top-heavy, which causes balance problems. Lower weight means your two-to-ten legs are less likely to sink into soft, wet, soil and get stuck.
You need power. The robots you see in those really cool videos doing balancing tricks, etc. usually have cables running to an external power source. The M1 Abrams main battle tank uses a gas turbine engine that gets about 0.6 miles per gallon of fuel and has a 500 gallon (1900 liter) fuel tank.
Your mecha needs a power plant that is more fuel efficient and far lighter. Lighter because otherwise the whole thing is top heavy and therefore harder to balance and more prone to falling over. Batteries won't pack enough power and will take too long to charge, so you're going to need a more exotic source of energy. Fusion reactors? Can you miniaturize those enough AND keep them stable under combat conditions? And this power plant needs to deliver more power than your tank's engines. Because wheels and tracks are more energy efficient than lifting and moving limbs, in general, so your mecha requires more power to move the same distance at the same speed relative to a tank of the same weight.
You need some sort of exotic armor. The Abrams tank uses steel, ceramics, and depleted uranium for its armor because of the material's density. You need a material that's lighter and thinner. Lighter because weight matters (see above). Thinner, because you don't have a big box to armor. You have comparatively spindly legs to armor. Spindly legs that need to move around, not just be hauled by tracks.
You need lightweight weapons, to whatever extent possible. This reduces the overall weight of the vehicle. And it would be best to avoid massive cannon like a main battle tank's main gun. These weigh in at about 1200 to 3300 kg and require cooling systems, recoil absorption systems, and other ancillary (and heavy) sub-systems. The recoil of a main battle gun might topple over your mecha. So you need lighter, faster, munitions. Lasers maybe? They won't require you to pack around tons of depleted-uranium ammunition, at least! And they might produce less heat and less recoil, maybe? The Abrams carries 42 rounds for the main gun, plus machine gun ammunition. You need more than this to outperform a tank.
The Abrams tank crew is four: a commander/machine gunner, a gunner, a loader, and a driver. Your mecha needs space for its entire crew. With better weapons and computers, maybe you can reduce the crew requirement to two, a driver and a gunner/commander? But they require space, air, food and water for campaigns, and safety systems. They are piloting a machine that has not just typical tank motions to deal with (driving fwd/back/steering plus turret controls) but also balance-related issues. Maybe your computer system can automate some of that, but you still have to account for the differences in complexity and comfort. Please provide some padding to absorb the shocks from foot-falls at speed that your crew will experience.
Your mecha stands tall and proud. Typical trope-approved mecha are at least 30 feet (9.1 meters) tall. For comparison the Abrams tank is 8 feet (2.44 meters) in height. Guess which one is easier to spot coming towards your defensive position? So your mecha has to have some technology(ies) to counter their target profile. They are easier to see at a distance, so you need stronger defenses against targeting systems. Heat shielding to block night vision and heat-seeking missiles, for example. And better armor, because they're going to take incoming fire sooner and therefore longer than a comparable tank. And higher maneuverability, because a fast-moving target is harder to hit. Camouflage may be pointless for something so tall, but it might help? I am not sure, but if you don't want tanks to be superior, this will need to be dealt with, somehow.
The published operational range of an Abrams tank is 265 miles (426 km). Your mecha should be able to go further between refuels (see Engines, above), and, to outperform tanks, needs to carry more firepower and/or greater ammunition reserves than that tank (see munitions, above). All while packing enough supplies for the crew. Because otherwise, your mecha is going to spend more time waiting on the supply vehicles to catch up than actually fighting.
How often is your mecha shut down for routine maintenance? How easily/quickly is it repaired? What percentage of "common" maintenance issues can be handled by the crew while under fire or otherwise cut off from specialized maintenance personnel and tools? Can they do any kind of improvised maintenance in the field, or is your mecha so super-advanced that it requires specialized equipment to do anything on it? How likely is it to suffer damage that necessitates taking the unit out of service? Your mecha must be more dependable than a tank or other comparable weapons platforms.
While not a critical requirement, one of the complaints against the Abrams is that it was designed from the ground up as a tank-killer. That's what it does best and everything else is basically just a condiment on that all-American hamburger patty.
If your mecha platform can be configured for different roles without compromising any of the above concerns (roles like scout/recon, heavy weapons, urban combat, anti-aircraft, etc. etc. etc.) then it has an advantage over tanks. Maybe the weapons systems are modular and can easily be swapped out between heavy tank-killer systems and lighter, faster, anti-aircraft platforms for example. Or maybe the lighter weapons give it greater speed and range for scouting purposes?
This is where the feet (or treads) meets the road. Is your mecha more maneuverable than a tank or other weapons platform, across the same or a wider array of terrain types? I've alluded to this in several of the above points, but this is the make-or-break one. Tanks have their problems with terrain -- they can be stopped with highway barriers. Any mecha worth the name will step over such paltry defenses with ease. Tanks can't cross water without serious and complex adaptations (or other vehicles). They can get mired in a few feet of mud.
But your mecha can get stuck too. Sandy soil, or extremely wet soil will cause problems for a mecha. They can sink into wet soil easily, since their full weight rides on anywhere from two to ten or so legs. That's a small contact area compared to the full treads of a tank. I've seen tracked construction vehicles sink to midway up the cab in soft soil and they're far lighter than a tank. What will your mecha do, on those comparatively tiny feet?
You might can hand-wave some of the various problems with mecha, but this one cannot be ignored. Otherwise, your mecha will be a non-moving weapons platform, waiting to be destroyed via aerial bombardment or an infantry soldier with a portable rocket launcher of some sort.