You all know about Bradman’s batting average of 99.94.
Here, we look at the other end of the spectrum.
This data is updated to 27-5-2022. Matches involving the ICC XI are not counted.
As per the usual practice, a minimum of 20 innings is considered.
Lowest Test batting averages (below 5.00):

Heading this list is current Bangladesh player Ebadot Hossain with 0.72.
Next lowest is Zimbabwe’s “Pommie” Mbangwa with 2.00, and JV Saunders of Australia long ago with 2.29
Bangladesh has another candidate coming up with Khalid Ahmed with 7 Tests, 11 innings and batting average of 0.50.
Current players here include Ebadot Hossain, Abu Jayed, Lahiru Kumara, Shannon Gabriel, Lungi Ngidi, and “Fizz” Rehman.
The lowest by Indian players are 3.80 by Maninder Singh, 4.07 by BS Chandrasekhar and 4.60 by DR Doshi.
Now we look at the corresponding figures for ODIs.
As before, we take a minimum of 20 innings. Matches involving the ICC XI, Asia XI and Africa XI are not counted.
Lowest ODI batting averages (below 5.00):

Here, the figures are slightly better with the lowest by Zimbabwe players B Muzarabani (2.81) and CB Mpofu (2.85).
Current players include B Muzarabani and N Pradeep (4.37).
From India there are S Sreesanth (4.00) and Ishant Sharma (4.80).
Also note Mohammad Irfan, the only 7-footer to play in Tests.