I had the same issue although not in ranked.

I hit an opponent twice and they should have received massive damage, but no damage was taken by them, and they had no counters to it. The Arena has been hacked and the developers don't care.

Second time this week I've fought players in the negative.

The dude's screenname was "Alan" in a cloaked, hooded figure. He went negative HP and kept going. Had some nice animation gifs at his disposal, i.e. clinking champagne glasses to congratulate me on "winning" the game, even though it continued with him at negative HP. He was also able to summon a very cool looking little red avatar that looked like a D&D Beholder creature. Eventually had to concede the game, since I couldn't win.

Look at Card Cloudsteel Kirin

I had them at -30 and I still lost.

YUP they're still here hacking. Had a match this week in which the opponent had -67 health and 35 poison counters. The photo is several turns after they should have died/lost.

Looking at you Stazi13 you loser.

It kind of reinforces that they don't give a **** in that there is no convenient or clear method of reporting this behavior.

Just went through a 40min and he just went more and more negative without dieing. When he finally killed me off he said good game. So frustrated

It literally just happened to me too. He was able to play until I ran out of health

This happened to me but i ended up winning. after researching i found that there are many hacks and third party programs and most are free to download. this means that mtg arena is full blown full of hackers and modders. make no mistake these people are cheating. there was no card to stop him from taking damage, and i would have just killed him. he turned his third party program on got no damage, then turned it off next round in hopes to killing me. lucky i had an enduring angel in my hand and then managed to defeat him next turn. the guy even boasted good game before he thought he was going to win. LOL these hackers have no skill either. they can`t even win most of the time with their hacks running. i spent 20 bucks on the game so far, and am never spending another cent on it. if wizards do not care about protecting their real player base. then they will have no real player base left. this game needs to be fixed. they are happy to take your money. but they do not care about you in the slightest.

Same

I face certain players that take no damage when I swing full , no blockers, and I cant understand why. No cards in play that protects it. Then a turn later I can do damage again. I there something I am missing or is this a thing others have had also?

It's starting to make me wonder if these are some type of "Cheat" Bots. Like maybe some players found an exploit/hack?? or worse, is the game Devs putting cheat bots in to prevent us from advancing, so that we have to buy more goodies from the store. Or just some bug. But, support is ignoring it for now.

This happened to me twice now. I opened a ticket with support, and they sent me this response and closed it:

"We understand that you are seeking help with a rules question. Wizards of the Coast offers numerous ways to help players understand how to play Magic: The Gathering, including resources collected on our Help Center article Magic: The Gathering Rules Questions, however we do not offer direct support for specific rules-related questions."

Last night, I knocked this guy down to -44 with and he lived 3 rounds in negative life points, and then beat me because all my creatures and cards tapped. WTF!?

I thought maybe this is some ability that I did not understand, but it seems like a bug/exploit. Anyone have any insights?

same happened to me today did not get screen shot, opponent did not have any other cards that would allow to not lose, guy was an A hole enough to through out the "Good Game " snark afterwards

Same

I just had the same thing happen to me as well

I lost to an opponent that played platinum angel in ranked historic

Yup... Just happened to me.. Luckily he conceded and I finally won the match!

i dont even know what to say, this makes this game so frustrating