In a 1v1 format like Standard, giving your opponent a card so you can use the creature right away is a downside, but this blue enchantment from Bloomburrow creates the opportunity for lucrative political deals in Commander
The biggest issue with Atraxa is that you'll sometimes play against an opponent that simply doesn't use counters
Similarly, once an ability of a colorless permanent has triggered an additional time due to Echoes of Eternity's first ability, giving that permanent one or more colors won't remove that additional triggered ability from the stack
Disgusting with extra combats
For example, if two creatures you control with lifelink deal combat damage at the same time, Enduring Tenacity's first ability will trigger twice and you may choose a different opponent for each trigger
Arena Championship 9 The next Arena Championship is coming