Relay contact arcing is a big problem for noobs, "muh why did my Arduino/Raspberry Pi crash?". The radiated EMI generally causes havoc, especially WiFi mains remote stuff ESP8266 sitting an inch away.
Back in the day we used snubbers, when there was room and the cost was minor. I always put them in but the parts are huge and frowned upon. You don't see them in appliances like ovens, dishwashers, furnace, A/C etc. they just let the relays arc and have a short life.
I find any back-EMF diode will experience maximum whatever the inductor current was, and whatever the supply voltage is.
After all, you can't get more current from an inductor than what was flowing in the first place, unless you are Nikola Tesla
If the relay coil current was say 100mA then even a 1N4148 is adequate.
But the back-EMF diode significantly extends the time for the B-field to decay (relay contacts to open) so a poor choice when you need speed.
Automotive will also just put say a 680R resistor across the coil, to pass the reverse-battery requirement yet have tame spikes.
edit: the relay coil-to-contact capacitance is another path for contact's arcing EMI to get to VDD on your MCU.