OFDM with beamforming
The interference you cause to the other user is determined by:


The total transmit power of your transmitter
The gain of your beampattern in the direction of the other user
The path loss to the other user
If the other user uses receive beamforming, then also by the gain of its beampattern in the direction of the transmitter


So if you transmit with a power of 10dBm, have a gain in the users direction of -20dB and a pathloss of 60dB, the other user receives -70dBm of interference power from the transmitter. Whether or not this is bad then depends also on how powerful the useful signal of the other user is.

More information is required here for a more detailled answer.