user11144: Just plain silly.
Replace all pieces of Black (except the king — you are not Chuck Norris, you must have one) with queens. The starting position is then a Mate in 3 (#3).
Challenge: Replace only a few Black pieces with queens such that Lichess (or your favorite engine) shows a forced mate in n, with n as high as possible. Of course, it is always a forced mate in a higher sense, since already replacing a rook is -7. For the record, I managed a #6.

user26472: Improved set-up:
Stockfish gives this one #-13:
[Title "Mate in 13"]
[FEN "rnbqkbnr/qqppppqq/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.d4 Qgxd4 2.e3 Qxd1+ 3.Kxd1 Qc5 4.Nc3 Qd6+ 5.Ke1 Qxc2 6.Nge2 Qbxb2 7.f3 Qcd2+ 8.Bxd2 Qdxd2+ 9.Kf2 Qbxc3 10.h4 Qdxe3+ 11.Kg3 Qg7+ 12.Kh3 Rxh4+ 13.Kxh4 Qeh6#

Original Mate in 9 (multiple lines):
[FEN "rnbqkbnr/pqppqqqp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. Nh3 Qbxg2 2. Bxg2 Qxg2 3. Rf1 Qh4 4. d3 Qxf1+ 5. Kxf1 Qxh3+ 6. Ke1 Qxf2+ 7. Kxf2 Qdh4+ 8. Kg1 Qxh2+ 9. Kf1 Qh1#


11144: <p>Just plain silly.</p>
<p>Replace all pieces of Black (except the king — you are not Chuck Norris, you must have one) with queens. The starting position is then a Mate in 3 (#3).</p>
<p>Challenge: Replace only a few Black pieces with queens such that Lichess (or your favorite engine) shows a forced mate in <em>n</em>, with <em>n</em> as high as possible. Of course, it is always a forced mate in a higher sense, since already replacing a rook is -7. For the record, I managed a #6.</p>
 26472: <p>Improved set-up:</p>
<p>Stockfish gives this one #-13:</p>
<pre><code>[Title &quot;Mate in 13&quot;]
[FEN &quot;rnbqkbnr/qqppppqq/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1&quot;]

1.d4 Qgxd4 2.e3 Qxd1+ 3.Kxd1 Qc5 4.Nc3 Qd6+ 5.Ke1 Qxc2 6.Nge2 Qbxb2 7.f3 Qcd2+ 8.Bxd2 Qdxd2+ 9.Kf2 Qbxc3 10.h4 Qdxe3+ 11.Kg3 Qg7+ 12.Kh3 Rxh4+ 13.Kxh4 Qeh6#
</code></pre>
<p>Original Mate in 9 (multiple lines):</p>
<pre><code>[FEN &quot;rnbqkbnr/pqppqqqp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1&quot;]

1. Nh3 Qbxg2 2. Bxg2 Qxg2 3. Rf1 Qh4 4. d3 Qxf1+ 5. Kxf1 Qxh3+ 6. Ke1 Qxf2+ 7. Kxf2 Qdh4+ 8. Kg1 Qxh2+ 9. Kf1 Qh1#
</code></pre>
