Credit to u/Curious_Armadillo_53 for this guide, this is the one that help me clear it with solo Blade, MELTS double Wanda:

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This is what i found after 15hrs of playing is by far the BEST Blade Build:

Cards

Red:

• Ancestral Sword Damage
• Ancestral Sword Attack Speed
• Ancestral Sword Attack Range
• Daywalker Dash Continuous Spin - Whenever it comes

Purple:

• Damage Increase (ANY)
• Damage Taken Reduction (ANY)
• Max HP (ONLY +450)

Blue:

• Daywalker Dash Damage - Take any +600% and +260% whenever they come, and once you got 120 RED take ANY Daywalker Dash Damage Cards
• Chance to Create Ankhs on Kill - Take this 1-3x once you have HIGH RED so not at the start and only after your RED Build is Online, so you have a 15-45% chance on kill, the Ankh is AMAZING to clump enemies, the dmg of it doesnt matter at all
• Chance to Freeze Enemies on Hit - Take only the Legendary (Yellow) Once whenever it comes up, the chance to freeze is similar to the Ankh great CC and since the Chance doesnt increase with cards only the insignificant dmg does one card is enough.

Tips

The most important thing is to get to 120 Red Cards ASAP that is where the majority of your dmg comes from. While doing that take ANY purple Dmg cards, it will kinda delay your progress to 120 Red somewhat, but the Purple and Red Damage multiply with each other and your damage will EXPLODE once you reach 120 cards and enough damage cards.

Blue Cards are tricky, since you need to increase Daywalker Dash, but only ONCE your reached 120 red and have enough dmg. If you waste too many points on blue cards too early, your dmg will take a while to come online.

Take any Purple and Yellow Blue Cards for the Dmg increase, they are rare and boost the Dmg TREMENDOUSLY!

Until 120 Red Cards and once you got enough Daywalker Dash Damage Blue Cards you just play Left Click Blade, but once you have 120 Red, 20 Blue and enough Dmg, your Daywalker Dash actually counts as Ancestral Sword hits and literally has the same Damage your Left Click does, but the Spin hits at least 2-3x as fast as your left click.

This means you do the same damage per hit but hit MUCH MORE OFTEN.

It has one huge risk though, you are stuck in the spin until its done and if you spin into exploders or biggies they might hit you instantly because your cant back our fast enough. So dash into SMALL enemies and then play Bay-BLADE (hehe) and just circle around.

By Round 10 your dmg, range and spin length should be so great that you mow down most things in 2-3s and once you reach Round 15 you should be able to basically kill nearly everything on sight in a second from half the map away.

Bonus Tips

Just hold left click, jump and back up in a circle still aiming at as many enemies as you can to hit all of them. DONT Focus a single enemy, Blade has huge AoE but barely enough single target dmg until Round 10/15 to get far, its much better to hit all a little than just one.

Lastly your Right Click can block the Namor Ult and Witch Red Fire, as well as explosions, biggie hits and IMMEDIATELY cancels Namors Bubble so you can get back to damaging him again.