Bangalores Ultimate

Bangalore's ult does damage and it will hurt you badly if two of them hit you at the same time. It will be 80 or 84 damage if you are hit by two of them.  (40 or 42 damage each)

However, people consider her ult bad mainly because it slows your own teammates down if they are hit by the explosion. Another issue is we can't tell who's ult it is. You need a mic to ask if that is friendly or foe. Those two things are the bad things about her ult. 

Don't use it to kill people. It's not for that.