Focusrite Scarlett 2i2 4th Gen with Beyerdynamic DT 770 Pro 80 Ohm
Loud enough for everyday listening, with little spare for peaks. The Scarlett 2i2 4th Gen reaches about 110.5 dB on the DT 770 Pro 80 Ω. Published numbers only.
The Focusrite Scarlett 2i2 4th Gen will play the Beyerdynamic DT 770 Pro 80 Ω loudly enough for most days. What you do not have is a comfortable reserve when the music suddenly gets much louder.
The DT 770 Pro 80 Ω is 80 Ω. Reaching a 110 dB peak — a loud moment in film or classical, not a casual average — takes about 1.42 V from the source. The Scarlett 2i2 4th Gen gets to 110.5 dB on this load.
Separately, the output impedance is 50 Ω into 80 Ω headphones. On a dynamic driver that ratio can lift or dull the bass. It is a note about tone, beside the loudness result, not a replacement for it.
On compressed pop you will not notice. On classical or a film mix the volume control will sit high. Buy a headphone amp if you want those peaks clean. Do not buy one because someone said every 80 Ω headphone is impossible from an interface — that is not what this pair does.