Well, you could theoretically set positive inbound fees in that channel to disincentivize routing (in LND, enabling the experimental configuration accept-positive-inbound-fees).

However, this seems to be causing some issues because peers that do not support inbound fees may be unaware of the added cost and will therefore fail to route through that channel without ever noticing why.

Another thing you could do is use the HtlcInterceptor RPC to intercept the HTLC and let it through only if you are happy with the fees you will earn from the outgoing channel.